Undead Lizardmen are weird. As the name suggests, they're just a few Undead versions of Lizardmen units, and their primary special quality is honestly that they get treated as Undead and Lizardmen for various purposes: you have a piece of gear that benefits Undead as a whole, and another one that benefits Lizardmen as a whole? Equip 'em both and Undead Lizardmen will benefit from both. Nonetheless, they actually have two unique factional Abilities. Odd stuff. The first is...

Necro Lizardman
+50% Poison resistance, +15% Ice resistance, -15% Fire resistance. +50% Attack at night and/or underground, immune to mental effects, and takes 50% more damage from 'holy' attackers. Effects that impose bonuses or penalties on Undead or Lizardmen apply them to Undead Lizardmen as well.

... a clear variation on the Undead Ability, though Undead don't have a standardized weakness to Fire, it's just common.

The next Ability is...

Ancient Rage
Anytime this unit takes damage (Except from counterattacks), its Attack increases by 10% and its crit chance by 3, up to a maximum of +50% and +15, respectively.

... basically a weak Rising Fury. (Raising Attack is usually going to be weaker than raising base Damage)

 Note that Tirexes don't boost the Morale of Undead Lizardmen, even though Undead Lizardmen are supposed to benefit from anything that benefits Lizardmen. I've... not exhaustively tested what benefits Undead Lizardmen and wouldn't be surprised if the in-game claim that they benefit from everything that benefits Undead and Lizardmen is not particularly true in practice.

 And while nothing in the game explicitly says so, Undead Lizardmen are in fact healed by Zlogn and otherwise behave as Undead as far as most healing effects don't work on them and so on. This includes that Plague gives them a Morale bonus, so feel free to mix them alongside Necromancers.

Conversely, they do not increase the chance of Zlogn being generated when a stack is wiped out, unlike regular Undead. You can mix regular Undead with Undead Lizardmen to make it possible, and of course when fighting Undead they'll be providing Zlogn drop chances for you, but if you're fielding Undead Lizardmen by themselves or alongside Neutrals/anybody else that isn't regular Undead you may find yourself wanting to cast the Zlogn Spell to support Vengeful Gorguls, Ram-Thors, or Necroxes.

Morale-wise, Undead Lizardmen are...

-3 Morale for Dragon presence in allies.

... the logical intersection of Undead and Lizardmen: they hate dragons, and that's it.

And yes, dragons hate them back just as hard. Because Lizardmen.

 As a whole, Undead Lizardmen are content lifted from Red Sands, though it's not as close in details as you might expect from some of the other Ice and Fire content that's pulled from Red Sands. In particular, Ancient Rage is not an Undead Lizardmen thing in Red Sands! Instead, they're broadly resistant to Spells and to Rage moves, which has the interesting impact of emphasizing the importance of your army over Rage and Spells. It's actually a bit disappointing that Ice and Fire gave them Ancient Rage instead -Ancient Rage really isn't that different from Adrenaline, in terms of making a faction of units pick up in effectiveness even as the battle goes on and they take casualties.

 So anyway, units.

Vengeful Gorgul
Level: 3
Hiring Cost: 350
Leadership: 110
Attack/Defense: 18 / 18
Initiative/Speed: 6 / 3
Health: 90
Damage: 8-10 Physical
Resistances: 15% Physical, 50% Poison,-15% Fire, 15% Ice
Talents: Running (Charge: 1. +2 Action Points), Ritual Dance (Reload: 2. Attacks all adjacent units, friend and foe alike, for 7-9 Physical damage, and inflicts Curse for 3 turns on all hit units. Selects a single target that can potentially retaliate)
Abilities: Necro Lizardman, Cursed Spear (Melee attack can strike two targets at once, with no risk of friendly fire. Inflicts Curse for 3 turns, except against Undead), Rugged Scales (Takes halved damage from non-magical ranged attacks, plus 15% Physical resistance), Horde (+1 Attack and Defense for every 30 members of the stack, to a max of doubling base Attack and Defense. So to a max of +18/+18 in this case), Vengeful (When below half of original size, the unit always crits), Tireless Warrior (Allied Undead Lizardmen all gain +1 to Initiative), Ancient Rage

Note that a rather funny bug is that Ritual Dance is, like Bloody Madness, actually supposed to inflict Bleeding, but is bugged so this doesn't happen... and its description doesn't mention this intended quality, so the lack doesn't look like a bug from the perspective of playing the game.
Anyway, basically take a Gorgul, make it less blazingly fast in turn order, but make it overall a beefier fighter. And remove the need to die horribly before you can perform a spin attack, but also remove the Bleeding infliction. (Due to a bug, but shhh) And get rid of the insanely aggressive Bloodlust in favor of Vengeful and Tireless Warrior. And the standard Undead Lizardmen traits, of course.

 Also note that, curiously, they have 2 less Attack but 2 more Defense compared to Gorguls. And of course their resistance setup is overall better, with a weaker weakness, stronger Physical and Poison resistances, and one more positive resistance overall.

 Vengeful Gorguls are perfectly good units, but they're not particularly new. They're probably a little better than Gorguls if each is looked at in isolation, but in real terms you'll mostly care about what the rest of your army is. If you're wanting a Gorgul sort of unit while you're running Undead, assuming you haven't maxed Persuasion already, then Vengeful Gorguls are the way to go. If you're wanting to run a more regular Lizardmen army that includes Gorguanas, the living Gorguls are the way to go, especially if you're wanting to use Whisper of the Creator. (It doesn't work on Vengeful Gorguls) Or if you want a Gorgul-y unit but you'd like it to be strongly resistant to Poison and/or hold up better against Ice damage, then Vengeful Gorguls are the way to go. Or if you want a Gorgul-y unit and it's really important it's immune to mental effects; Vengeful Gorguls. Or if you want a Gorgul-y unit and it's important it's susceptible to mental effects (Maybe you want to slap Berserk on it, I dunno), then living Gorguls. But broadly? They play very similarly, other than Gorguls potentially getting extra turns from Bloodlust while Vengeful Gorguls can toss out a no-retaliation splash melee attack without needing to lose half their numbers and all.

 So there's... not a lot to actually say about Vengeful Gorguls. They're an okay unit, and they work for adding something to the game, more or less, but it doesn't really give me a lot of nuance to talk about.

Gorguana Ghost
Level: 3
Hiring Cost: 590
Leadership: 145
Attack/Defense: 20 / 22
Initiative/Speed: 5 / 2
Health: 80
Damage (Ranged): 7-11 Magical
Damage (Melee): 4-7 Physical
Resistances: 50% Physical, 50% Poison, 25% Magic, -15% Fire, 15% Ice
Talents: Mark of Blood (Reload: 3. A single target enemy takes doubled damage from all sources for 2 turns), Teleportation (Reload: 3. A target ally is instantly moved up to 3 tiles away from its current position to a location of the caster's choice)
Abilities: Necro Lizardman, Magic Missile (Range: 6), Shackles of Darkness (Ranged attacks have a 50% chance of locking off access to the target's Talents for 2 turns. Level 5 units are immune), Phantom (50% Physical resistance, and can pass through most terrain), Magic Protection (25% Magic resistance), Antimagic Aura (Allied Lizardmen within 2 tiles gain 10 points of Magic resistance), Ancient Rage

Take a Gorguana, turn it into a Ghost, and then make it moderately resistant to the usual Ghost answer of Magic damage. Okay, and replace Whisper of the Creator with Teleportation, but that's more generalized, so hey.

Stats-wise, they really are basically a slightly upstatted Gorguana, though also with their Leadership raised enough that they're actually a little behind when it comes to eg damage output. And they'd be behind on durability except they have pretty bonkers resistances. Though... they're also actually lacking Horde, so their offense is a bit low when compared to Gorguanas and their survivability is leaning on their ridiculous suite of resistances to get by. And Gorguanas already have iffy offenses!

 Note that Antimagic Aura doesn't benefit the Gorguana Ghost itself. This includes that separate stacks of Gorguana Ghosts won't bolster each other.

 Gorguana Ghosts are a bit more distinctive from Gorguana than Vengeful Gorguls are from living Gorguls, thankfully. They're much tankier, and thanks to being healed by Zlogn you can even get away with taking some casualties and just undoing them with a Zlogn. This makes them useful as emergency meatshields for other, more fragile ranged units. Ancient Rage means they'll even hit harder after all that's said and done! Shackles of Darkness, though unreliable, means their ranged game is a bit less focused on raw damage (Since they can't really hope to compete with Gorguanas there) and more on trying to restrict key targets. Alternatively, you can focus on Mark of Blood and Teleportation; Gorguana Ghosts can help get key targets out of the fight, whether by Teleporting a fast melee unit close enough to block in a ranged unit or Mark of Blooding something to then nuke it. (If possible, try to save Rage or Spell nuking for after Mark of Blood is on someone, if you're intending to use it that turn. And remember: even percentile effects double! A Viking can wipe 60% of a stack, guaranteed, with Hel the Messenger) Gorguana Ghosts are overall a bit more splashable than Gorguanas, even considering how widely Undead Lizardmen impose Morale penalties.

 Though do note they lack Bloodlust and so are badly inferior at cleaning up summon spam or any other case of groups of weak stacks. This is one of the biggest advantages regular Gorguanas have over them, as while Bloodlust isn't fully reliable Gorguans are still one of your best options for cleaning up even widely-spaced cases of weak stacks. This can be quite important when dealing with unit types that have at least one Talent not affected by stack size, such as Dryads or Demonesses, and even outside that being able to clean up a stack that's in the way of one of your melee stacks and possibly immediately do something else of use is a big deal. Gorguana Ghosts tend to outperform Gorguanas when you're dealing with eg 5 equally-sized stacks where none of them is a summoner or equivalent, but it's much more biased toward Gorguanas when summons get involved or when attacking castles or any other situation where there's a large number of stacks that's widely spaced.

Ram-Thor
Level: 4
Hiring Cost: 1800
Leadership: 280
Attack/Defense: 30 / 40
Initiative/Speed: 2 / 2
Health: 220
Damage: 16-20 Physical
Resistances: 20% Physical, 50% Poison, -15% Fire, 15% Ice
Talents: Ram (Reload: 2. Runs directly in a straight line to hit a target with no chance for retaliation, and inflict Bleeding for 1 turn. Distance is current action points+5. Base damage is 16-20 Physical damage, but each tile traveled increases this by 20% of base), Displacement (Reload: 3. An enemy below Level 5 takes 17-22 Physical damage and is knocked back 1 tile, with no chance to retaliate)
Abilities: Necro Lizardman, Triple-horned (Melee attacks strike enemies to the side of the target as well, but has no risk of friendly fire), Sharp Horns (Melee attacks always inflict Bleeding for 1 turn), Rugged Scales (Takes halved damage from ranged attacks, plus 20% Physical resistance), Spikes (Automatically retaliates against melee attacks for 8-15 Physical damage, infinitely), Wide Plate (Adjacent allies below Level 5 gain 20% Defense), Ancient Rage

Take a Brontor, remove its Burrow/ranged attack gimmick, and then make it a little more viable as a regular melee unit. Though note they've actually got one less Initiative than regular Brontors. They're pretty heavily reliant on Ram or support -and whaddya know, Gorguana Ghosts can Teleport them into position! Convenient, isn't it?

Ram-Thor's battle model isn't as different from the Brontor as the portrait would suggest -no glowing eyes, for one- and in fact in certain lighting conditions they're basically indistinguishable from a Brontor. It's... kinda annoying, actually.

 Unfortunately, you really need to support Ram-Thors to get reliable use out of them, and in particular due to how Trapper and Tactics interact even on open fields Tactics is unreliable for ensuring they can Ram to get to the other side first turn. Displacement is also... kinda gimmicky, as the Ram-Thor itself doesn't want enemies moved away from it, will have trouble pursuing if they decide to head elsewhere, goes so late in turn order it's unlikely to be able to take the opportunity to enter the now-unoccupied space without assistance, and in spite of Displacement hitting harder than its basic attack if you're doing things right it will usually be inferior to taking advantage of Triple-Horned's splash on basic melee. Displacement is only really useful as a way of eg shoving enemies into Traps, and if you're doing things right you've probably gotten Trapper maxed by the time you have Ram-Thors -and even if you haven't, there's other, more generally useful options for shoving enemies where you need them, such as Cyclops. On top of all that, Displacement doesn't inflict Bleeding!

 I like the idea of the Ram-Thor, but in practice it mostly tends to be a Brontor But Bad, and the AI in particular is really bad at using it. They won't use Ram unless they start the turn lined up with a target -which is true of Brontors as well, but Brontors only have 1 Speed anyway so it usually doesn't matter- and they're obsessive about using Displacement even when it hurts them and they don't even try to get moved to be lined up for a Ram in future, all of which means it's pretty trivial -given how late in turn order they are- to get your units positioned so they don't get to do anything for several turns. And it gets even worse if you start moving fast fliers back to their side of the battlefield, so they end up deciding to turn around!

 The mass Bleeding infliction is pretty cool, at least, and is in actuality probably the biggest argument for considering Ram-Thors. There's other options for inflicting Bleeding, but not for inflicting it en mass, not in Ice and Fire, and mass Bleeding is pretty amazing for supporting Spell-slinging, Rage-slinging, and just generally killing things dead through a combination of percentile damage and the fact that all non-percentile damage's effectiveness is increased against Bleeding targets. It's still clunky to get the Ram-Thor into position, but mass Bleeding is potentially worth the effort. If only for the novelty value.

Also, note that while the game describes Ram in a manner that makes it sound like it's an infinitely long charge, in actuality it's a variation on the Viking shield charge Talent, just one with +5 to the maximum tiles traveled instead of +1. This isn't hugely important on most battlefields, but it can trip you up if you try to set your Ram-Thor all the way into the back of a standard battlefield opposite from an enemy that will move after the Ram-Thor (Or won't move at all, for whatever reason), and whoops the Ram-Thor will actually stop just short of the target. It's also a very meaningful limitation on some of the rarer long battlefields, where even Tactics 2 might not be enough to let the Ram-Thor Ram something on the first turn, and notably it means that without action point gifting or Speed boosting the Ram-Thor caps out at +120% damage on Ram.

Oddly, the Ram-Thor is another undead unit that secretly has the 'real' Persistence of Mind Ability, making its protection against mental effects more properly complete. No other Undead Lizardman has this quality.

Worm
Level: 2
Hiring Cost: 20
Leadership: 15
Attack/Defense: 7 / 2
Initiative/Speed: 6 / 3
Health: 6
Damage: 1-2 Poison
Resistances: -10% Physical, 50% Poison, -15% Fire, 15% Ice
Talents: None
Abilities: Necro Lizardman, Burrow (Movement ignores all intervening terrain and units, and a ranged attack can be performed. Attack range: infinite), Poisonous (30% chance to inflict Poisoning for 3 turns), Drain Life (Drains health when attacking, healing itself for 100% of damage dealt and potentially undoing casualties), Eyeless (Immunity to Blind, Precision, and Greasy Mist. Also can detect invisible creatures), Ancient Rage

 Basically a Gobot or Adult Gobot, but all Undead-y. And doing actual Poison damage on its attack, which has its situational advantages (eg they'll tend to do better than a Gobot against Knights) but is probably mostly a disadvantage. They've technically lost some Abilities, but most of them are covered by being a Necro Lizardman (eg Persistence of Mind), except for No Melee Penalty... which the fact that it's not listed is strange, as Worm melee damage is in fact identical to their ranged damage. This similarity to living Gobots extends to Worms secretly being unable to miss in melee for whatever reason.

 And yes, the Worm lacks the Worm Ability, somewhat ironically.

 The awesome fact that they leech at a distance makes them a surprisingly decent ranged attacker for doing stuff like momentarily blocking an enemy and then Burrowing to safety to plink at enemies to get their numbers back up. It's a really neat concept, and it's too bad this is the only game they show up in.

 Worms are one of the more faithful-to-Red-Sands Undead Lizardmen, at least once you account for the differences in overall Undead Lizardmen handling. Just a few fiddly details like the Red Sands version doing doubled damage to Dragons. The basic idea of an undead Gobot that has Drain Life and can Poison enemies is essentially the same.

 As enemies, Worms should generally either be ignored until other enemies are dealt with or made a high-priority target. Just halfway ignoring them while splash damage catches them is letting them leverage their leech to be a problem, and lets Ancient Rage bolster them to boot. I personally prefer to focus them down, as they're almost never paired up with anything that's particularly more problematic to not focus on first, but I suppose it in part depends on what kind of force composition you've got and all.

 As player units, Worms are a really nifty unit. There's stronger ranged attackers, but Worms are really nice for not having every minor bit of damage be irritating, as minor casualties will be undone if you're not fighting the Undead. You can't even access Worms until you're past the most Undead-heavy parts of the game, so while Worms are less appealing when you're trying to do the endgame they have a decent stretch of game to be performing well! They're also a huge beneficiary of Items that directly boost damage, such as the Snowball Regalia (+1 Ice damage to your units) or the Weapon that among other things adds +1 Ice damage to your units. Ice and Fire has a decent selection of such Items, too, so this is highly relevant. If you're considering doing a swarm-y army leveraging such Items, Worms are an excellent unit to include in such a lineup, ending up with insane damage -which makes it even easier to leverage their capacity to tank hits and heal it off!

Winged Shadow
Level: 4
Hiring Cost: 490
Leadership: 180
Attack/Defense: 35 / 28
Initiative/Speed: 5 / 5
Health: 140
Damage: 9-15 Physical
Resistances: 30% Magic, 50% Poison, -15% Fire. 15% Ice
Talents: Embrace of Death (Reload: 2. Does 17 Magic damage to an adjacent target with no chance of retaliation. Up to 60% of the damage is used to heal/resurrect the Winged Shadow stack, assuming the target is a living organism and not a Plant), Scream of Darkness (Charge: 1. All allied Undead Lizardmen gain +1 Speed for 2 turns)
Abilities: Necro Lizardman, Flight, Sharp Beak (If the Winged Shadow is flying in a straight line for at least two tiles before attacking, the hit is a crit), Magic Protection (30% Magic resistance), Wings of Darkness (+1 Morale to all allied Undead Lizardmen), Ancient Rage

Bizarrely, even though the Winged Shadow's portrait only appears to have a different background from the Highterant, the actual battle model is quite obviously different, looking like some disturbing Facehugger thing. Pretty much the opposite of the Ram-Thor's situation.

 Compared to a Highterant, Winged Shadows are more of a bulky support unit, clearly meant to be placed in a mono-Undead Lizardmen army, rather than being a fairly generic flying attacker that happens to be able to generate copies of itself in a chain. They actually have 1 less Speed and Initiative -though Scream of Darkness directly makes up for the Speed, kinda- and overall their attacking stats aren't really as good when you consider that they're 30 more Leadership than a Highterant, but on the other hand Embrace of Death lets them fill a role akin to Vampires and Ancient Vampires, if a bit more clunkily.

 The fact that Embrace of Death does Magic damage can be useful for letting Winged Shadows contribute decent damage against Physically resistant threats like Knights, which is a bit of an advantage over Highterants.

Overall, though, Winged Shadows are just... Highterants that are a little worse overall but have more advantageous resistances and a different Talent for keeping survivability up. There's not a lot to say about them, and personally I think Highterants tend to be more useful/threatening in real terms unless the opposition is doing Poison damage.

Necrox
Level: 5
Hiring Cost: 20,000
Leadership: 2400
Attack/Defense: 52 / 55
Initiative/Speed: 5 / 4
Health: 1000
Damage: 90-130 Physical
Resistances: 25% Physical, 50% Poison, -15% Fire, 15% Ice
Talents: Primal Fear (Reload: 4. All enemies who are below the Necrox's stack's Leadership and are not immune to mental effects take 20-50 Physical damage per Necrox and also have their current Action Points halved), Eat Corpse (Reload: 2. Destroys an adjacent corpse, fully healing the 'top' Necrox and resetting the stack's Action Point total), Terror (Reload: 4. A target enemy below Level 5 flees 2 tiles away from the Necrox. If they're susceptible to mental effects, Fear is inflicted for 2 turns as well)
Abilities: Undead Lizardman, Rugged Scales (Takes halved damage from non-magical ranged attacks, plus 25% Physical resistance), Aura of Suppression (All enemies within 2 tiles that are below Level 5 and are susceptible to mental effects suffer -1 Morale), Frightening (50% chance to inflict Fear for 2 turns with melee attack. An attack that successfully inflicts Fear cannot be retaliated again. Level 5 units are immune), Predator (The Necrox automatically consumes the corpse of any stack it finishes off, benefiting as if it had used Eat Corpse, but without affecting the actual Talent's reload state), Morphing (When initiating an attack, the Necrox gains a 2-turn buff that provides 20% of the target's base Attack and Defense. This effect cannot trigger again until the existing buff fades), Ancient Rage

 It's a Tirex, but with even more horrifying amounts of resistance, and replacing the Morale boost to allies with more offensively-oriented supporting effects. Also their Primal Fear reloads much slower, which is a bit surprising.

MAJOR BUG NOTE: This identicalness to Tirex includes that a Necrox finishing off a Burrowed Brontor or a Sheeped unit will crash the game. So don't do either of those.
And yes I'm aware the English version's in-game name is 'Necrohs'. I'm not using that. The internal files call it a Necrox, Red Sands calls it a Necrox, and 'Necrox' is obviously 'necro+Tirex'. 'Necrohs' is an obvious mistranslation, and a rather weird one.

 Terror is a bit more powerful than it first sounds, because it will eat the target's turn if they have an upcoming turn. It can still work on a unit whose turn is already over, too, unlike some other Talents that can eat the target's turn, though it won't eat their next turn in that case. It's also occasionally wonky; the unit is supposed to flee from the Necrox, but occasionally they'll charge toward it instead, particularly if their current position means that fleeing 2 tiles backwards would place them out of bounds. This usually isn't a significant flaw, but it's worth keeping in mind, especially if you're trying to use Terror to shove a unit into a Trap.

 Morphing is a largely-irrelevant gimmick. It does mean you should ideally have Necrox hit high-Leadership units like dragons before low-Leadership units like Fire Dragonflies, but the impact is sufficiently low regardless you can largely ignore it. It's a bit disappointing and weird.

Overall, you can treat a Necrox as a fairly directly improved version of the Tirex, aside the part where the Tirex provides a Morale boost to allied Lizardmen. The Necrox's increased Leadership means its raw stats aren't going as far in real terms, but its resistances are better, it has an array of useful immunity from being Undead, Morphing does partially offset the stat issue, and Terror is really useful. The main point in the Tirex's favor is the fact that you will pick up a bunch of Tirex eggs from the Lizardmen area and so be able to field Tirex for free, where Necrox cost actual money to purchase initially/undo casualties.

 Weirdly, the Ice and Fire Necrox actually has very little to do with the Red Sands version. The Red Sands version was a unit that was very late in the turn order -only 3 Initiative- but had Spell immunity and instead of Terror it could animate the dead. It didn't have Predator, Rugged Scales, or Morphing, nor for that matter Ancient Rage since that's just an Ice and Fire Lizardman thing. So instead of being a kind of Tirex+, it was really its own separate thing, and honestly a lot more interesting. I'm not sure why Ice and Fire did this.

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 One thing worth noting is that as far as I'm aware you'll never see a shop selling Undead Lizardmen outside the Marshan Swamp. And I've never seen any shop selling them aside the Frogus castle, at that. Maybe they're actually rarely sold by other sources, but if so I've yet to see it.

 As such, without abusing Sacrifice your supplies when you get the Frogus Castle offering units is all you'll ever have, I'm fairly sure. It certainly simplifies keeping track of where to go when restocking on Undead Lizardmen, but the Frogus Castle's stock is, in my experience, not going to last you to the end of the game without Sacrifice shenanigans. It also means staying stocked is a huge pain, at least until you've defeated the Giant Undead Lizardmen and so can access the Marshan Swamp directly from Greenwort. (... which you can't do until after you've completed all of Prince Guilford's Quest objectives, because you're arbitrarily barred from advancing the whole Lizardmen/Marshan Swamp plotline until you're able to talk to Archmage Rezo in a friendly way) Undead Lizardmen feel rather tacked-on, in general. (Which is a bit odd, since they're lifted from Red Sands, where the Snow Elves are almost completely original to Ice and Fire)

An additional issue here is that initially the Frogus Castle will only have three different types of Undead Lizardmen, and it's possible to permanently lock yourself out of the ability to expand its roster. You'll be asked to go find Frogus Squelch and make nice with him: when approached, he'll ask you to kill his brother. If you tell him no you won't do that, his brother isn't evil or anything... that's it. You've screwed yourself out of ever accessing more types of Undead Lizardmen. You have to accept the 'go kill my brother' request to be able to expand your arsenal, even though you don't have to actually go through with the killing! I'm pretty sure this is some manner of bug, but in any event, remember: when Squelch asks you to kill his brother, say yes.

If you are going to insist on giving Undead Lizardmen a proper chance, you'll probably want to get a hold of Necromancers so you can leverage their free recruitment of low-end Undead. You can then Sacrifice those Undead to bolster your Undead Lizardmen numbers without meaningfully costing you gold. Fortuitously, Necromancers work decently well with Undead Lizardmen anyway.

The other issue with making use of Undead Lizardmen is how late they are. If you play the game reasonably naturally, even if you make a point of prioritizing the Ice Garden/Cave of Mysteries for clearing out as feasible, you're not going to get a hold of Undead Lizardmen at all until something like 70% of the way into the game. And it'll take still longer to get relatively convenient access to them, as you can't unblock the Marshan Swamp until after you're done with the plot-minimum elements of Demonis!

Even if you know exactly what you're doing and are willing to heavily abuse the ability to sneak past battlegroups and accept severe casualties in attacking severely out-of-depth fights... it will be a huge pain and still take a surprisingly long time to make happen. Initial access to the Marshan Swamp won't open up until you've completed the primary Lizardmen quest chain -which first requires talking to the Snow Elf king so you're even allowed to fight your way into the Cave of Mysteries, and then requires you do multiple Hero fights in the Cave of Mysteries that are tuned to be pretty rough fights even by the Cave of Mysteries' standards... and then you still can't actually complete this quest chain until you've unlocked access to Demonis, which itself requires punching through a minimum of four relatively tough fights in Darion. And completing the quest chain, such that you unlock the Marshan Swamp entrance in the Cave of Mysteries, still requires you complete a specific fight in Demonis -or more precisely, in Hades.

All of which means there's unavoidably a frustratingly limited portion of the game you can use Undead Lizardmen in, a quality not really shared with any other faction. Even Dwarves, whose actual home territories cannot be accessed until still later, are more accessible in real terms, because there are several shops dotted throughout the early-to-midgame that will have Dwarves, and still others that are allowed to have Dwarves even if it's not guaranteed. It's frustrating, and it's particularly strange because Undead Lizardmen are mostly not designed as a super-faction.... which is a particularly striking contrast with Snow Elves, who are vastly more accessible (You can unlock the Ice Gardens the instant you have access to Istering, which is firmly in the early game) and yet are packed with much more in the way of incredible tools.
By a similar token, to the best of my awareness you'll only ever see enemy battlegroups containing Undead Lizardmen in two cases; one, they're all over the Marshan Swamp, often mixed with Undead. Two, there's a couple of battlegroups that show up in the Cave of Mysteries over by the entryway to the Marshan Swamp. (You have to do some sidequesting to actually gain access to it, unfortunately, and it involves going to Demonis first) It's... pretty frustrating, as it would've been nice for Ice and Fire to have diversified the late game by mixing Undead Lizardmen into Undead battlegroups, and it would've made narrative sense to boot. Or Ice and Fire could've incorporated Undead Lizardmen into enemy battlegroups right away and made it a bit of a mystery ("I've never before seen some of the creatures marching among the dead. Where do they come from?"), and again helped make Warriors of the North a bit less repetitive with its heavy use of Undead battlegroups.

 It's probably the most disappointing aspect of Ice and Fire, as there's a fairly obvious opening to do beneficial stuff and... it just wasn't taken.

 Alas.

 Next time, we get started on Spells in Warriors of the North, starting with the Chaos school.