
Where in The Legend you had four 'Spirits of Rage' that each leveled separately and each had four skills, with 'rest' periods denying you access to four specific skills at a time, in Armored Princess your Baby Dragon is the only element to Rage. One experience bar, one set of 9 skills. (Technically down from 12 in The Legend, but the actual variety is up due to a lack of redundancy across Spirits) Notably, this means Rest periods greater than 1 completely deny you access to Rage for the number of turns in question... unless you take advantage of Awaken Dragon, of course. On the other hand, there's no longer dealing with the weird meta-management issue of trying to feed experience to a given Spirit, which is nice.
One of the more significant yet non-obvious changes Armored Princess makes to Rage is that it alters Rage 'rot' to be noticeably slower. Back in The Legend, it wasn't particularly realistic to try to build Rage in one fight to then carry it into another, presumably-harder fight to use there, because unless the two units were extremely close the Rage would usually drain to zero, or at least to something like 2 Rage, before you got into that second fight.
On the other hand, it can make actual play extremely tedious, as the net result is that you spend a lot more time waiting for your Mana to refill if you don't use Fast Travel or manually refill you Mana. Fortunately, this issue tends to fade as you get further into the game for various reasons, but it can be fairly off-putting when you're first getting into the game and don't yet know it'll get better.
At the beginning of the game, you're asked to choose between colors for your Baby Dragon. Which color you pick provides a minor stat bonus, chooses which Rage ability other than Crushing Blow they start with, and changes the Baby Dragon's appearance. The options are...
+1 Initiative to animals and Dragons. Begins with the Mana Accelerator Rage ability.
The best choice. While its benefits depend on you using certain kinds of units, they include a lot of useful units. Critically, the benefit doesn't drop off in importance, yet is powerful at the very beginning of the game, particularly as you're more-or-less guaranteed to get Royal Snakes early on, which are already an excellent unit.
+5 to max Rage. Begins with the Mana Accelerator Rage Ability.
Well. It's an option, I guess. I'm not sure why you'd pick it, unless you were picking form over function, and even then the Red Baby Dragon doesn't look as good as the Blue.
+1 Attack. Begins with the Ball of Lightning Rage ability.
I like the Alien Baby Dragon's appearance (okay that's not actually it's name, I just wish it was), but +1 Attack is terrible, and it's not the only source of Ball of Lightning. There's not really any reason to pick it other than aesthetic.
+1 Intellect. Begins with the Treasure Searcher Rage Ability.
+1 Intellect is not great, but it's useful in the early game, and this is the only Baby Dragon that starts with Treasure Searcher. Getting Treasure Searcher early is definitely nice, but I don't think it's really worth the sacrifice of the Blue's Initiative bonuses. Still, it's the alternative I can most see a decent argument for, such as if you're doing a challenge run that for whatever reason refuses to use animals and Dragons.
+1 Defense. Begins with the Stone Wall Rage Ability.
NEXT.
... +1 Defense is awful -you should always be endeavoring to avoid taking damage in the first place, and 1 Defense is so tiny its effect will always be drowned out by damage variance- and Stone Wall is less useful than just killing things so they can't hurt you, unless you're doing shenanigans against badly out-of-depth foes. In which case you probably will level to get it naturally from a different Baby Dragon anyway. It's tied with Treasure Searcher for earliest-to-unlock Rage Ability anyway, so you're not even getting Stone Wall notably early.
+2% chance for units to get a critical hit. Begins with the Mystic Egg Rage ability.
Literally the only reason I can see to consider this is if you think Mystic Egg is a gamebreaker at the beginning of the game.
It isn't, by the way.
+5 to max Mana. Begins with the Ball of Lightning Rage Ability.
Again, just take Blue. It's more useful to anyone who's concerned with spending Mana. The primary advantage it has is that Ball of Lightning takes a bit to show up (Level 9, the latest of any of these), and 5 max Mana is more useful than a point of Attack.
------------------------
Ultimately my biggest disappointment with the colors mechanic is that I initially thought, from the way the game framed it, that whatever Rage ability a color got was impossible to acquire through leveling. That would've made for an interesting and nuanced set of choices, and given the game an extra layer of replay value. As-is, it's in this nasty sourspot: if it were just affecting the color, then you'd pick what you liked and that would be a cool touch, if totally irrelevant to gameplay. Instead it's badly balanced so that there's only really one color that makes sense to pick for mechanical reasons, rendering the others basically wasted art asserts, not to mention all the other labor that went into setting up the option to choose a color in the first place.
That disappointing start thankfully fails to set the tone for the Rage system in Armored Princess. In basically every other regard, the game has drastically improved Rage!
Note that the 'required level' on some upgrades/unlocks is the required level of the Baby Dragon, not of Amelie.
Also note that experience mechanics work much like they do in The Legend, just Rage has only one experience meter instead of four separate ones. The main change beyond that is that class-based experience modifiers have been made less impactful; instead of experience being 100%/80%/50% for Warrior/Paladin/Mage runs, it's 100%/90%/70% for Warrior/Paladin/Mage runs. Not that the Mage had that much difficulty leveling Spirits in The Legend, mind, but hey. In any event, this is the last time this component of experience is changed; Warriors of the North and Dark Side retain 100%/90%/70% for their red/green/blue class or character choices.

Crushing Blow
Basic stats
Damage: 90-100 Physical
Rage: 4
Experience: 3
Pushback: 1
Crushing Blow involves picking a single target with a direction attached. That target takes Physical damage, and if it's below Level 4 it also gets pushed in the direction you picked some number of tiles. It's reasonably useful to think of Crushing Blow as an attack performed by a unit, said unit happening to be your Baby Dragon, as a lot of similar rules apply: you can't attack 'from' occupied tiles or out-of-bound locations, influencing your options for pushing, and also meaning a fully surrounded unit is actually not targetable. You don't have to worry about Traps stopping your Baby Dragon, so it's not fully comparable, but it can help acclimate you to Crushing Blow's rules.
Crushing Blow itself is Armored Princess' basic single-target Rage attack that you start the game with, comparable to Zerock's Smashing Sword or Sleem's Poisonous Spit, only it's actually good.
Part of this is that it has better damage scaling, starting roughly comparable to Smashing Sword in raw damage but rapidly climbing from there. The other, bigger part is that it has the utility effect of pushing a target built in. This can be used to delay slow-but-problematic stacks (eg Bears, Ancient Bears), shove enemies out of melee range of your ranged attackers, push an enemy into a chokepoint to prevent other enemies from passing through, shove recalcitrant enemies into Traps you intended for them to walk into that they instead walked around.... Crushing Blow's utility is tremendous, largely limited by your own creativity.
Damage 1 Upgrade: Damage: 130-150, Rage: +1, Experience: 5
Damage 2 Upgrade: Damage: 200-300, Rage: +2, Experience: 8
Damage 3 Upgrade: Damage: 400-500, Rage: +3, Experience: 13, Pushback: 2
Damage 4 Upgrade: Damage: 800-900, Rage: +4, Exp: 19 (Requires Level 10)
Damage 5 Upgrade: Damage: 1300-1400, Rage: +5, Experience: 26 (Requires Level 14)
Damage 6 Upgrade: Damage: 1900-2000, Rage: +6, Exp: 34, Pushback: 3 Rest: +1 (Requires Level 18 )
Rage 1 Upgrade: Rage: -5 (Requires fifth Damage upgrade)
Rest 1 Upgrade: Rest: -1 (Requires final Damage upgrade)
Final stats
Damage: 1900-2000 Physical
(+25%)
Rage: 20
Experience: 34
Pushback: 3 (+1)
Rest: 1
Crushing Blow has a fairly simple, straightforward progression, aside from the Rest increase you then cancel and the Rage decrease. You just do more damage and occasionally get greater pushback.
The parentheses are because of this Item:

The Lizardmen Combat Boots, which boost Crushing Blow's damage and pushback by the listed values when equipped. I'm noting it at all because normally Rage attacks can't be modified by anything except Rage levels. I'll similarly be covering the other Rage skill-boosting Items where relevant.
The expense climbing can be a bit frustrating, but overall so long as you're not, say, upgrading it every time the game offers it, the Rage cost should be manageable, especially if you make sure to not delay Anger overly much. (Remember: Anger is available to all three classes in Armored Princess, not just the Warrior)
Eventually Crushing Blow's damage becomes genuinely lackluster, but unlike The Legend's basic attack effects that time is a long, long way off, and it really does help tremendously that it has the push effect. 3 tiles of push is honestly ridiculous, allowing you to keep one unit out of the fighting entirely essentially indefinitely (There's not many units that breach 3 Speed), or slow down two slow units basically at once. The damage may cease to impress eventually, but the push remains tremendously useful forever.

Treasure Searcher
Basic stats
Chests: 1
Altars: 0
Rage: 4
Exp: 5
Rest: 1
When a battle starts, the game generates pre-determined spots on the battlefield. When selecting Treasure Searcher, you will be able to select from these spots, and the Baby Dragon can then fly over and dig up whatever is underneath. Chests are represented with green tiles, while 'altars' are represented with blue. Diggables cannot be accessed if the tile is currently blocked in some manner (usually, by a unit occupying it), and in the case of chests the player will still need to have units manually collect them if they want the contents.
'Altar' is the game's strange term for digging up neutral objects that normally occasionally spawn on the battlefield, such as the statues that like to Bless, Heal, or Divine Armor a random nearby unit. That particular functionality is sort of interesting, but not terribly useful. The chest part is a lot more nifty, shoring up your Gold supplies and occasionally throwing in Magic Crystals, or even cooler stuff like Spell scrolls and free Runes!
I especially appreciate how Treasure Searcher gives you something useful to do with Rage when a battle is winding down. It was always a little frustrating in The Legend how battles would tend to eventually reach a point where you had a decent supply of Rage, but the enemy was no longer worth bothering to hit with Rage, and yet due to how rapidly Rage drained out of battle in The Legend it didn't actually make sense to hold onto the Rage for later use. Treasure Searcher is, in fact, ideally used at the tail end of a fight.
Notably, Treasure Searcher is not really comparable to any Rage skill from The Legend, which is a bit unusual for the list.
Treasure 1 Upgrade: Chest: 2 Altar: 0 Rage: +2 Experience: 8
Treasure 2 Upgrade: Chest: 2 Altar: 1 Rage: +3 Experience: 12
Treasure 3 Upgrade: Chest: 3 Altar: 2 Rage: +4 Experience: 17
Rage Upgrade: Rage: -5 (Requires final Treasure Upgrade)
A weirder progression than Smashing Blow's, and shorter.
Broadly speaking, it's usually best to take the first upgrade and then neglect upgrading Treasure Searcher until much later in the game, if at all. The second Chest is fantastic, whereas opening up 'Altars' is more-or-less worthless, and bumping up the Rage cost is a problem, especially early in the game before you've had the chance to max Anger.
Final stats
Chests: 3 (+1)
Altars: 2 (+1)
Rage: 8
Rest: 1
Why +1? Because of this:

The Shovel! It increases the number of Chests and 'Altars' you can dig up by one apiece. An additional Chest at no Rage cost increase is very, very nice.
That said, while Treasure Searcher is something I appreciate Armored Princess introducing, I'm perfectly glad the following games abandoned the basic idea. Treasure Searcher having strategic benefits at the cost of tactical utility is this weird, somewhat problematic dynamic, and Armored Princess doesn't really delve far enough in that direction to make it a good mechanic. Playing 'optimally' means repetitively and tediously digging up 2-3 chests per fight instead of using your fun and powerful Rage moves to actually help with the fight, and even though in the long haul the benefits add up any given chest is probably not that important so the whole thing feels like a grind.
I appreciate it as an experiment, but not in execution, basically.
To be more specific, the chest contents work out to:
72% chance to get gold
15% chance to get random regular Spell Scrolls
5% chance to get Magic Crystals
5% chance to get 1 random Talent Rune
3% chance to get a random Wanderer Scroll
In the case of Talent Runes, you're looking at equal odds of any given one. (ie it's not, say, biased toward Might Runes for a Warrior run) In the case of Magic Crystals, you can get one (50% of the time), two (30% of the time), three (15% of the time), or five (5% of the time) Magic Crystals from a given chest.
In the case of regular Spell Scrolls, you can get 1-3 copies of a Scroll from a given chest; 80% of the time it's one Scroll, 15% of the time it's two Scrolls, and 5% of the time it's three Scrolls. This never mixes Scrolls; you can find 2 Fear Scrolls from a chest, or 2 Magic Shackles Scrolls from a chest, but you'll never get a Fear Scroll alongside a Magic Shackles Scroll.
I'm honestly a little puzzled by Wanderer Scrolls being the rarest possibility, and not Talent Runes. Talent Runes are by far the best payout and the biggest reason why optimal play involves always digging up and collecting every chest. Wanderer Scrolls have their uses, but they're just not as valuable as Talent Runes -there's a reason every game in this series makes it so that buying Talent Runes is an option, but limits it with rapidly escalating costs.
Regardless, even the gold is important for a surprisingly long time if you play on higher difficulties; you really should be leveraging Treasure Searcher as fully as you can if you're playing on a difficulty that challenges you at all.
Which is a bit unfortunate, as I've already covered.

Stone Wall
Basic stats
Health: 150
Defense: 20
Rage: 6
Exp: 7
Rest: 2
Stone Wall works much like Zerock's Stone Wall from The Legend, only it 'curves'. It's still a 3-tile wall, you still have to be able to place all three tiles' worth or you can't place it at all, and it's still a single object where attacking any of the three tiles does damage to the same HP pool and running that pool out clears out all three tiles.
I don't usually use Stone Wall much, myself. While its progression is better than Zerock's Stone Wall had, it's still a bit underwhelming, and it's hampered by the changes to Rest making the high-for-Armored Princess Rest period particularly egregious a flaw. In fact, in some ways it's actually worse off than Zerock's Stone Wall, because this Stone Wall has actual competition from your other Rage skills -if setting a Stone Wall is just going to delay that Swordsmen stack one turn anyway, why not Crushing Blow it to delay it one turn while doing damage and probably generating more Rage experience and not having a Rest period of 2?
Whereas Zerock's Stone Wall was his only skill that could be used to delay enemies, and so if your other Spirits were Resting the fact that Zerock had it could actually be useful.
Health 1 Upgrade: Health: 250, Rage: +1, Experience: +2
Health 2 Upgrade: Health: 500, Rage: +2, Experience: +3 (Requires Level 11)
Health 3 Upgrade: Health: 1000, Rage: +3, Experience: +4 (Requires Level 14)
Health 4 Upgrade: Health: 2000, Rage: +4, Experience: +5 (Requires Level 17)
Health 5 Upgrade: Health: 5000, Rage: +5, Experience: +6 (Requires Level 23)
5000 Health is pretty darn solid, though again I personally don't really feel Stone Wall is worth it.
Defense 1 Upgrade: Defense: 30, Rage: +2, Experience: +3
Defense 2 Upgrade: Defense: 40, Rage: +3, Experience: +4 (Requires Level 13 )
Defense 3 Upgrade: Defense: 50, Rage: +4, Experience: +5 (Requires Level 18 )
Since Defense is effectively a Health multiplier, these boosts tend to be more worth pursuing once you've gotten the Health up fairly high. Which leads back to the issue that I don't really feel it's worth pursuing in the first place.
Final stats
Health: 5000 (+50%)
Defense: 50
Rage: 30
Experience: 39
Rest: 2
You guessed it, it's the

Shovel again. Yes, it simultaneously boosts both Stone Wall and Treasure Searcher. That's fair, given Stone Wall is difficult to justify using, just from the Rest period of 2 and the whole 'why make walls when you can kill and/or shove and/or Shock things' issue.
Ultimately the Rest of 2 really is what makes Stone Wall so difficult to justify, less because a Rest of 2 hurts so much and more because Stone Wall is a bad form of Rage effect for being more than 1 Rest. Lava Call's Rest 2 is annoying, but if you're expecting it to help you finish the battle this turn or the next turn it's not an issue at all. Stone Wall's whole point is dragging a fight out, not hurrying it to a conclusion. Awaken Dragon contributes to the issue: an alpha-strike of using Lava Call and then a 1-Rest nuke via Awaken Dragon is a way to cram a lot of damage into one turn, with Lava Call's Rest of 2 being eliminated by these shenanigans. There's not really an equivalent thing for Stone Wall. Like, yes, you can throw up a Stone Wall and then use Awaken Dragon to do some 1-Rest action, but there's no actual synergy involved.
You shouldn't completely forget it exists, but it really is probably the worst Rage move in the list.

Ball of Lightning (Requires Level 9)
Basic stats
Damage: 10-15% Magic
Shock chance: 20%
Rage: 15
Experience: 10
Rest: 1
Ball of Lightning is a strange hybrid of Lina's Gizmo and Reaper's Soul Draining. When used it generates a unit high in the air over a targeted empty tile (The need for it to be an empty tile is usually not important, but can matter if eg on a small battlefield and summoning a lot of units), which will of its own volition go and attack a single target (It seems to prefer high HP or high Leadership stacks, thankfully, and though it has a movement limit of 5 tiles I've never seen it ignore a target to go haring after something further away. On the other hand, it also, rather bizarrely, has a strong preference for avoiding hitting the same target twice in a row, even if there's exactly one stack that is far higher than any others) inflicting percentile damage to the stack. (ie a stack of 100 units will suffer damage equal to 10-15% of their total Health, regardless of whether they're Peasants or Cyclops) The Ball of Lightning will do this three times total, once a Round, before fizzling out. You can have multiple Balls of Lightning on the field, but while they don't compete with regular units for space they do compete with each other for space. (ie if one stack has a Ball of Lightning hovering over it, any other Balls of Lightning will elect a different target when their 'turn' rolls around) Plus they compete with Gizmo, as previously covered. The ball itself has an Initiative of 10, and so will go before all regular units unless fairly significant Initiative boosting is involved.
Ball of Lightning itself starts out fairly worthless -it's simply far too expensive for the damage it'll be dealing, compared to say Crushing Blow- but as it gains levels and your ability to generate Rage climbs, Ball of Lightning becomes increasingly useful for helping you take on out-of-depth fights effectively (Whether this is you fighting a Sea Chart guardian, a difficult Quest-fight, or simply taking on a Keeper force earlier than your forces are strictly ready for) and also just becomes a useful catchall tool for burning Rage when no other option has more immediate, obvious utility. (eg no enemy is in a good position to be maneuvered in a useful way by Smashing Blow)
Well, until its Rest period goes up, anyway.
Also note that though Ball of Lightning is percentile damage, there are damage modification effects it interacts with. Most notable is Blood Mark on Gorguanas, which flat-out doubles damage on a target -when Ball of Lightning can potentially do 48% damage. 96% damage isn't strictly an instant kill, but it will leave even massively outsized stacks very manageable if it happens.
Another useful quirk of Ball of Lightning is that it can actually generate Rage for hitting things! As such, it can be a useful 'filler' choice just for the fact that it will directly recoup some of its cost over the three turns it's active.
As with eg Burn and Poisoning, Ball of Lightning being Magic damage of course means it does reduced damage to enemies with high Magic resistance -and increased damage to Guard Droids and Repair Droids, since they have negative Magic resistance. This makes it particularly appreciated for dealing with oversized droid stacks (With Mark of Blood, it might one-shot them regardless of size!), and makes it less worth using in fights heavy on enemies who have high Magic resistance. On the plus side, a number of Magically resistant units have poor enough base Health you'd probably be better off using a non-percentile Rage move anyway, but it can be an unpleasant surprise when taking on stuff like Witch Hunters.
One limitation on Ball of Lightning is that it doesn't work on Gremlins. It's still incredibly useful in Keeper fights, and since they can't be shocked and are heavily resistant to Magic damage it would be a bit wasteful, but if you were hoping to use a Ball of Lightning to wear down a Gremlin, it just won't happen.
Damage 1 Upgrade: Damage: + [0-5]%, chance of shock: +2%, Rage: +2, Experience: +4
Damage 2 Upgrade: Damage: + [0-7]%, chance of shock: +2%, Rage: +3, Experience: +6
Damage 3 Upgrade: Damage: + [10-15]%, chance of shock: +2%, Rage: +5, Experience: +8 Rest: 2 (Requires Level 26)
Notice that you don't raise minimum damage except on the last damage upgrade... which is also the one that raises the Rest period. And there's no way to reduce the Rest period via Rage leveling. This is fairly frustrating, since without minimum damage going up the RNG can always give you a low roll and thus you don't really benefit from the damage upgrade at any given moment.
If you're fond of using Awaken Dragon, the Rest period isn't too abominable, since you'd want to start with Ball of Lightning anyway due to its percentile damage. Ball of Lightning followed by Dragon Dive does more damage than the other way around, for example, so needing to put Ball of Lightning first isn't a burden in that case.
Shock 1 Upgrade: Damage: + [0-2]%, chance of shock: +6%, Rage: +2, Experience: +4
Shock 2 Upgrade: Damage: + [0-2]%, chance of shock: +8%, Rage: +3, Experience: +6
Shock 3 Upgrade: Damage: + [0-2]%, chance of shock: +10% Rage: +5, Experience: +8 (Requires Level 21)
In conjunction with the base values and also with maxing the damage upgrades, Ball of Lightning ends up with a 50% chance to shock. Since each Ball of Lightning use hits three times, that's actually fairly reliable -only 12.5% of the time will you fail to get a shock from a given usage of Ball of Lightning.
That said, it should still be treated as a bonus to be pleased by rather than an assumption to be planned around.
Final stats
Damage: 20%-48%
Shock chance: 50% (+30%)
Rage: 35
Experience: 46
Rest: 2
(Hits: 4)
The +30% Shock chance and the number of hits is because of...

... the Helmet with Antenna. It's a pretty neat Helmet, though be careful about its Initiative penalty; -1 Initiative to anything above Level 2 can turn a battle against you very strongly if the Initiative numbers align right. (Or wrong, if you want to look at it that way) Still, boosting Ball of Lightning never loses relevancy thanks to its auto-scaling nature. (Unless you push its price above your current Rage limit, anyway, but unlike some Rage skills this isn't a particularly big concern) Getting up to an 80% Shock chance is also reliable enough to be planning around if eg you only really need the Shock by turn 2.
Ball of Lightning is always held back by being a bit pricey, but overall it just gets better and better as you get deeper in the game and it becomes increasingly normal for enemy battlegroups to substantially out-Leadership you. And of course its utility rises if you play on higher difficulties, because the rising army sizes don't really matter to it.
I do find the last-second Rest increase frustrating, though. It's really not good for Armored Princess' design to handle Rest in this way.

Mana Accelerator (Requires Level 6)
Basic stats
Mana: 7
Action Points: 1
Rage: 8
Exp: 10
Rest: 1
Mana Accelerator is loosely comparable to Lina's Chargers, only it's actually good.
First of all, you get complete control over Mana Accelerator's location. Second of all, there's no randomization on what it gives: it just gives Mana, which is far more useful than being able to recoup some Rage. Third of all, you get to actually increase the Action Points it provides, making it a lot more consistently useful. Fourth of all, you only have to worry about it backfiring on you if you're an idiot, basically.
Early in the game, Mana Accelerator is fantastic for propping up your meager Mana supplies, particularly if you're inclined to try to delay battles to grind for Medal progress. Later on the Mana boost is less impressive, as your Mana needs tend to grow faster than its Mana generation, but Action Points never stop being useful and treating the Mana as a bonus when your primary goal was getting a unit into a really useful position works out just fine for keeping it really useful.
While you might intuitively expect Mana Charger's AP to be more useful to a melee-focused army, the ability to eg walk your Bowmen out of melee range even though they were pinned against the edge of the battlefield is not to be underestimated, often allowing ranged units to get out of awkward situations or avoid them entirely in the first place.
Mana 1 Upgrade: Mana: 10, Rage: +3, Experience: +2
Mana 2 Upgrade: Mana: 14, Rage: +5, Experience: +3
Mana 3 Upgrade: Mana: 19, Rage: +7, Experience: +4 (Requires Level 18)
Mana 4 Upgrade: Mana: 25, Rage: +9, Exp: +5 (Requires Level 23)
Action Points 1 Upgrade: AP: 2, Rage: +3, Experience: +5
Rage 1 Upgrade: Rage: -10 (Requires Rage Cost > 25)
Notice that this Rage down effect is greater than any single cost increase is. If eg you've already taken the AP increase and up to Mana 2, taking Mana 3 is effectively better than free in the long haul because you'll be offered the Rage down and end up 3 Rage less than before you took Mana 3. If you don't really care about maxing Mana Accelerator, pursuing this might be for the best.
Final stats
Mana provided: 25 (+3)
Action Points provided: 2 (+1)
Rage: 25
That's right, it's another Rage skill that benefits from an Item. In this case, it's the

Lizard Gloves. That's... all they do.
If you get them early, the boost to Mana is pretty nice, but in the long haul it barely matters, and the AP boost becomes a lot more situational once you've gotten the AP upgrade per se. You tend to 'grow out' of using the Lizard Gloves as a result, because they're a big deal toward the beginning of the game but will eventually be easily out-competed by other Gloves/whatever else you might be able to put in that slot they're occupying.
Mana Accelerator tends to slowly drop off in utility as your Mana needs climb and all, but it never completely stops being relevant, and early on it's genuinely one of the more amazing Rage skills you've got. You should keep it in mind the whole way.

Mystic Egg (Requires Level 4)
Basic stats
Leadership: 100, +50% of Hero's Leadership
Troop Level: 1-2
Rage: 15
Experience: 10
Rest: 2
Mystic Egg generates an egg in any empty tile you like on the battlefield, which the following turn hatches into a stack of a partially randomized type.
Really early in the game it's okay, because enemies can genuinely struggle to break the egg and what comes out is certainly useful as a distraction at minimum, but as Leadership values rise it rapidly falls behind.
Leadership 1 Upgrade: Leadership: 300, Rage: +3, Experience: +2
Leadership 2 Upgrade: Leadership: 700, Rage: +4, Experience: +3
Leadership 3 Upgrade: Leadership: 1300, Rage: +5, Experience: +4 (Requires Level 16)
These upgrades are basically worthless. Either you get them fairly early in the game and they're temporarily helpful for propping Mystic Egg up without fixing its core flaws, or you don't and they're never worth pursuing later on. I'd usually recommend ignoring them entirely if at all possible.
No, what matters later on is...
Hero Percent 1 Upgrade: Leadership of Hero: 70%, Rage: +5 Experience: +3 (Requires Level 9)
Hero Percent 2 Upgrade: Leadership of Hero: 90%, Rage: +7 Experience: +4 (Requires Level 13)
... the percentile upgrades.
Getting to 90% is necessary for Mystic Egg to be competitive late in the game, and it still suffers from the fact that the player expects to routinely be fighting forces that out-Leadership their own forces. Effects that either auto-scale to the enemy (ie Ball of Lightning) or bypass Leadership as a concern to some extent (eg the push effects on Smashing Blow and Dragon Dive) tend to hold up much better later in the game.
So... it's still bad, really.
But at least maxing this out ensures the amount is actually worthwhile.
Obviously, Mystic Egg works best on the Warrior and worst on the Mage, and this upgrade chain in particular is most beneficial to the Warrior and least beneficial to the Mage in turn.
Creatures 1 Upgrade: Level of Creatures: 1-4, Rage: +2, Experience: +3
Creatures 2 Upgrade: Level of Creatures: 2-5, Rage: +3, Exp: +4 (Requires Level 16)
One issue here is that Level doesn't correlate to unit quality in any kind of absolute sense. Higher Level units tend to be more mobile, and tend to require more damage to inflict a casualty in the first place, but that doesn't necessarily mean they're better. In fact, for a disposable unit that will be lost no matter how the battle goes, lower-Level units actually tend to be better at soaking damage in real terms due to their favorable Leadership-to-Health ratios, and similarly tend to dish out more damage in real terms. Being lower in Level means being more susceptible to myriad negative effects, such as the Beholder Paralyzing Ray, but there's no universal mechanic that punishes a unit for being low-Level.
So even though it's cool to be able to just spawn dragons from nothing, potentially, in real terms you're upping the cost on an already-pricey skill to make it even more random in a manner that isn't even necessarily beneficial in actual fact.
This really needed to either not be an upgrade at all or be reworked to be, you know, an upgrade.
As for specifics...
Initially, Mystic Egg can generate any of Venomous Spiders, Cave Spiders, Fire Spiders, Undead Spiders, Lake Dragonflies, Fire Dragonflies, Snakes, or Swamp Snakes. Once you've upgraded its Level range once, it gains Griffins, Royal Griffins, Royal Snakes, and Hayterants. The second and final upgrade removes the dragonflies and every spider except Fire Spiders, but adds Red Dragons, Emerald Green Dragons, Black Dragons, and Bone Dragons.
Yes, your egg can hatch into undead. It's a bit weird, especially when you consider that the name in the original Russian heavily implies the Baby Dragon is just stealing eggs, nothing magic about this. Admittedly Bone Dragon eggs are a thing in these games...
Final stats
Leadership: 1300, +90% of Hero's Leadership
Troop Level: 2-5
Rage: 44
Experience: 33
Rest: 2
Overpriced and not that useful. I honestly don't get why Mystic Egg was made so bad. What is even the point of making it Rest 2, anyway? I mean, this is something of a general problem with the game, that there's no clear design purpose to higher Rest values, but I'm clear the devs have this vague notion of Rest periods correlating to the power of a move, which rather implies the devs thought Mystic Egg is actually one of the stronger Rage skills. Which is just confusing.

Dragon Dive (Requires Level 12)
Basic stats
Damage: 300-600 Physical
Rage: 20
Experience: 10
Rest: 1
Dragon Dive involves selecting a single empty, valid-to-travel tile. All enemies take Physical damage, with the amount dropping off the further they are from the selected tile. Enemies can also be shoved one tile away from the target tile, but only if directly adjacent to the impact point.
Regardless, Dragon Dive spends a good chunk of the early/mid-game being your go-to damaging Rage skill, having better base damage than Crushing Blow while hitting literally every enemy. From what I can tell it actually experiences drop-off even for the directly adjacent tiles and so its damage is in real terms a little lower than it sounds, but it's still the case that you're likely to have a phase where Dragon Dive is cheaper than Smashing Blow while doing more damage overall. In the long haul Fiery Phantoms tends to shunt it aside, but you shouldn't neglect Dragon Dive, especially since it has the key advantage of being reasonably affordable up until it's fully upgraded. And even then 42 Rage is not nearly as difficult to keep up with than 70 Rage is. Even the Mage can expect to reach 50-ish max Rage soon enough to stay on top of Dragon Dive's cost growth.
The push effect is really useful early on as well, and at first glance it's easy to think it's just going to permanently shunt aside Crushing Blow, but as Crushing Blow gains push distance and Dragon Dive does not, in actuality they just change roles as you go forward: Crushing Blow becomes your go-to Rage move for manipulating an enemy's position, while Dragon Dive is about damage with a bonus of shoving a unit or two or three.
It's a bit unfortunate Dragon Dive's damage doesn't really keep up with endgame needs, but you'll spend a surprisingly long portion of the game getting plenty of use out of it, and doling levels out to it isn't any kind of waste given how many other Rage levelups are easy to just ignore without it being a problem. (eg Stone Wall and Mystic Egg as a whole)
Damage 1 Upgrade: Damage: 600-900, Rage: +9, Experience: 13
Damage 2 Upgrade: Damage: 900-1300, Rage: +10, Experience: 17 (Requires Level 21)
Damage 3 Upgrade: Damage: 1300-1700, Rage: +11, Experience: 22 (Requires Level 26)
Damage 4 Upgrade: Damage: 1900-2400 Rage: +12 Experience: 28 Rest: +1
Rage 1 Upgrade: Rage: -10 (Requires Rage Cost > 35)
In other words, this can be offered after you've taken the second damage upgrade while exactly canceling its cost increase. So the second damage upgrade is particularly easy to justify grabbing.
Rest 1 Upgrade: Rest: -1 (Requires Rest > 1)
ie you have to get its damage maxed, temporarily put up with a Rest of 2, and hopefully get offered this on your very next Rage level so you don't have to deal with it anymore.
Final stats
Damage: 1900-2400 Physical
Rage: 52
Experience: 28
Rest: 1
As I said, in the end Dragon Dive falls off in utility, but it's a very solid Rage skill for long enough I don't have any particular complaints in the end. It would be nice if it was useful in the endgame, but it keeps up much longer than most of the Rage skills in The Legend, so there's a clear improvement in the design there.

Lava Call (Requires Level 17)
Basic stats
Damage: 1000-1200 Fire
Targets: 3
Rage: 35
Experience: 10
Rest: 2
Lava Call hits several targets with no input from the player for high Fire damage. That's... all it does.
Damage 1 Upgrade: Damage: 1300-1500, Rage: +5 Experience: +2
Damage 2 Upgrade: Damage: 1800-2000, Rage: +6 Experience: +3 (Requires level 26)
Damage 3 Upgrade: Damage: 2300-2600, Rage: +7 Experience: +4 (Requires Level 31)
Damage 4 Upgrade: Damage: 2900-3200, Rage: +8 Experience: +5 (Requires Level 36)
Damage 5 Upgrade: Damage: 3600-3800, Rage: +9, Exp: +6, Rest: 3 (Requires Level 41)
One thing worth pointing out here is that Lava Call grows rather slowly in strength: the first damage upgrade is only a 30% increase to minimum damage, and less than that for maximum damage. It's often difficult to justify a level into its damage when you could get a much more dramatic boost in some other Rage skill.
Targets 1 Upgrade: Targets: 4, Rage: +8, Exp: +1
Targets 2 Upgrade: Targets : 5 Rage: +7 Experience: +2
Targets 3 Upgrade: Targets : 6 Rage: +6 Exp: +3
Targets 4 Upgrade: Targets : 7 Rage: +5 Experience: +4
I like how the Rage increase decelerates as you climb through the target upgrade list. 5 targets is the most consistently useful number, with the two past that being dependent on you fighting summoners or in a fight with an unusually larger number of stacks. (Which mostly means castle fights and Keeper fights) Or you can look at it in terms of how going from 3 to 4 targets is a 33% increase in your overall damage, 4 to 5 is merely a 25% increase, and so on. Either way, it's a pleasant surprise that the game correctly concludes those later increases shouldn't hurt the price as much.
Rage 1 Upgrade: Rage: -10 (Requires Rage Cost > 60)
Final stats
Damage: 3600-3800 Fire
Targets: 7
Rage: 86
Experience: 40
Rest: 3
Lava Call's three big problems go thusly:
1: It's pricey. If you fully upgrade it, it's actually your single most expensive Rage skill.
2: It's stuck with a Rest period above 1, in fact ultimately rising to a horrific 3! Unless you're going to immediately use Awaken Dragon or expect to finish the fight so soon afterward that you won't care about another chance at Rage, this is unacceptable.
3: Fiery Phantoms will usually be better. The only two points substantially in Lava Call's favor are that Lava Call has no friendly fire/can hit potentially all your enemies regardless of how they're spread out, and that Lava Call's Fire damage means it will hit especially hard against Plants.
The overall result is that Lava Call is... niche. This is compounded by the problem with Rage skills we saw in The Legend: if they suck, you'll tend to find yourself wanting to invest in the ones that don't suck, which just widens the gap between the skills that suck and the ones that are actually worthwhile. Maybe your Warrior has put a lot of levels into Fiery Phantoms, so many that even against Plants Lava Call's damage remains inferior. Suddenly all its got is the targeting behavior to its credit... and Dragon Dive has an even more generous targeting behavior, aside the damage drop-off.
Lava Call's unlock time and base cost also hurt it a lot. When you first get a hold of it, it's often a struggle to have enough max Rage to afford it even in theory if you're not a Warrior, and yet the damage by that point is merely solid, not the kind of thing that turns the tide of a battle all on its own. If you bolster its damage to make it more worthwhile, it climbs even further out of your reach. If you don't boost its damage, you'll occasionally be able to use it, but you won't be impressed with the results.
While I tend to consider Mystic Egg and Stone Wall not worth using, Lava Call is the only Rage skill I've found more or less unusable throughout the entire game. Mystic Egg and Stone Wall at least fill niches early on, and Mystic Egg scaling to your Leadership means it can still potentially pull its weight all the way into the endgame, where Lava Call's fixed damage means it's always falling behind.

Fiery Phantoms (Requires Level 25)
Basic stats
Damage: 1600-1900 Astral
Friendly fire: 80%
Rage: 50
Experience: 10
Rest: 1
Fiery Phantoms has you select a tile -it can be occupied- to center a 3-tile-outward Astral damage strike that hits everything inside the area. Friendly units will take damage, albeit somewhat-reduced damage.
And... that's it. Fiery Phantoms is straightforward damage that enemies can't resist.
That's enough, though.
Damage 1 Upgrade: Damage: 1900-2300, Rage: +10, Experience: +3
Damage 2 Upgrade: Damage: 2300-2700, Rage: +10, Experience: +4, Rest: +1 (Requires Level 31)
Damage 3 Upgrade: Damage: 2700-3300, Rage: +10, Experience: +5, Rest: +1 (Requires Level 36)
Damage 4 Upgrade: Damage: 3000-3700, Rage: +10, Experience: +6, Rest: +1 (Requires Level 41)
The progression is a bit slower than I'd prefer, damage-wise, particularly given the Rage cost increase means you're only barely pulling ahead in damage cost-to-damage efficiency, but if you can reliably pull off the Rage for Fiery Phantoms (Read: you're the Warrior) then these upgrades are absolutely worth pursuing. Not necessarily immediately, but at all for sure.
Rollback 1 Upgrade: Damage to Allies: 60%, Experience: +2 Rest: -1 (Requires Rest > 1)
Rollback 2 Upgrade: Damage to Allies: 40%, Experience: +3 Rest: -1 (Requires Rest > 1)
Rollback 3 Upgrade: Damage to Allies: 20%, Experience: +4 Rest: -1(Requires Rest > 1)
In short: except the first damage upgrade, each damage upgrade will unlock the opportunity to undo the Rest increase, while throwing in for free bonus experience gain and a reduction in friendly fire. If you're going to try to make Fiery Phantoms a seriously useful part of your arsenal, this is just obvious.
Rage 1 Upgrade: Rage: -10 (Requires Rage Cost > 50)
ie you can potentially be offered this if you've made any damage upgrades at all. Absolutely worth taking if offered, though you might prioritize other Rage options at any particular level.
Final stats
Damage: 3000-3700 Astral
Friendly fire: 20%
Rage: 80
Experience: 37
Rest: 1
Fiery Phantoms is at its best when you're fighting battlegroups that have a large number of closely-clustered stacks, such that you can hit 7 or more separate stacks. Against more ordinary battlegroups, it can be a cool alpha strike if you manage to get into a fight with a ton of Rage, but can be harder to justify the Rage cost. It's particularly useful for trying to kill eg Black Dragons, due to the Leadership-to-Health ratio -maximum power Fiery Phantoms is going to kill 7500 Leadership of Black Dragons (in a single stack, that is), where eg against Peasants it works out to somewhere below 3700 Leadership of units- where large stacks of low-Leadership units tends to be better to target with Ball of Lightning.
Fiery Phantoms ideally is supported by arranging for the enemies to remain clustered. A Chaos Dragon is a useful way to do this, since it resists Astral damage anyway and will be spreading Burn and all, or a Paladin with maxed Resurrection-the-Skill can hurl some unit into the fray and not care at all about the casualties they're taking. If you don't bother to keep enemies clustered to maximize the number of targets hit, Fiery Phantoms will tend to drop off in utility in the late game: if you're only going to manage to hit like two targets while fighting battlegroups containing stacks with 40,000 or more Leadership, Ball of Lightning will often do more damage right away, let alone over time, while throwing in free Shocks.
Fiery Phantoms is probably the main Rage skill that justifies considering drinking a Potion of Rage beforehand, since it's very Rage-intensive and generally works best on the first turn of a fight if you're not going to specifically lure the enemies together. Other Rage skills are either far easier to afford or are, well, not very good, and especially if you make sure to max Anger early it's usually easy to generate enough Rage simply through killing the enemy.
In any event, Fiery Phantoms holds up far better than eg Black Hole in The Legend, in spite of inferior targeting behavior, just because its damage is way, way better.
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Last of the relevant Items is the Dragon's Toy, made by combining the other four Items together. It has a decent, if somewhat boring, effect of providing +15 Rage when equipped, and more relevantly it boosts the damage of all damaging Rage skills by 15%. I'd usually rather equip most of the individual components, but the Dragon's Toy is worth noting for the fact that it's the only way to boost Dragon Dive, Fiery Phantoms, or Lava Call. If you find yourself spamming those skills a lot, and/or unable to reach the Rage necessary to use them at all while wanting to use them, it's definitely worth considering, and since you can always take it apart to get the components back, just using it temporarily, such as for a particularly difficult fight, can make sense.
Though, on an Item-related note it's a lot more worthwhile to keep in mind that Potions of Rage can be used to set yourself up for a fight in Armored Princess, simply because Rage itself is far more useful. This is counterbalanced by the fact that where The Legend was so generous with Potions of Rage my last Mage ended the game with more than fifty, having not ever bothered to buy any (Though admittedly also not bothering to use any), my last Armored Princess Mage had more like 15 and didn't see that many in stores because it's just way less generous with them. As such, it's a trickier judgment call as to whether it's worth blowing the Potion of Rage or not.
Which is actually nice! Tricky decisions are what you get if your game is genuinely nuanced and interesting.
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Next time, we break from The Legend's pattern and cover Medals.
See you then.