The most distinctive, interesting element of the Alien Hunters DLC is, of course, the Alien Rulers themselves, who have enough unique mechanics considerations I'll be covering them all at once instead of loading it into one of the specific Alien Rulers posts: they're going to be long enough as-is.

First of all, the Alien Rulers are one-of-a-kind boss enemies; you'll never see more than one of a given one at a time, and once you've killed a given Alien Ruler, that's it, you're never seeing it again in that run. Related to this is that Alien Rulers will attempt to retreat after a number of turns (8-14, depending on difficulty and how many times you've fought a given Ruler previously, with higher difficulties and later encounters increasing the number of turns it takes), or when you've knocked off a third or more of their maximum HP in that particular encounter, or when enough of your forces are Unconscious or dead. (2 soldiers, unless it's at least your third encounter with that Ruler in which case it takes 3 downed soldiers for them to leave) Fortunately, Alien Rulers retain all HP and Armor damage from your previous attempts, so you don't need to be able to kill them in one attempt. Given how high their HP is, that's pretty important.

Note that this retreat behavior occurs a limited number of times, with the final fight being to the death. If you're not playing on Legend, they'll fight to the death the third time you encounter them. (Legend makes it the fifth time) Their appearance is also only partially randomized; past the initial encounter (Which I'll get to in a minute) you'll get 1-2 missions of breathing room, with the second mission already being a 75% chance of them showing up on the mission. (Unless you're playing on Legend, in which case the second mission is a 50% chance, the third mission is a 75% chance, and then the fourth mission they're guaranteed to show up if they've failed to spawn the previous two times) As such, if you're not playing Legend once a given Ruler shows up they'll be dead or wipe a squad within 7 missions at most. 

I've personally never seen them spawn into Ambushes or a Chosen Stronghold assault, and suspect that's an actual limitation, but am not completely sure. They can spawn into the second-to-last mission, surprisingly. (As in, I've had it happen to me, personally, through a confluence of timing and impatience) I've yet to find a clean list of all mission types they're barred from internally, unfortunately, and it's difficult to be sure from just playing the game given how they won't show up very often in any given run. I may update this space later if I find such, or have them show up in a mission I suspected they couldn't.

They can spawn into an Avenger Defense, albeit it's unlikely to happen. I... doubt they can spawn into Chosen-caused Avenger Defenses, but don't have real proof they can't.


Their first encounter takes 2-and-a-half possible forms, depending on your initial settings. The first possibility is checking the Alien Hunters box when you start a campaign; in this scenario, the Alien Rulers will never spawn prior to you performing the Nest mission, which is a special mission that lingers forever until done (And is spawned by a chain of two Rumors that, themselves, linger until scanned) and will be where you first encounter the Viper King.

Possibility one-half is what follows; after the enemy force level reaches the point an Alien Ruler is placed in, you're going to encounter the Alien Ruler in short order in more or less any random mission. If you don't turn on Alien Hunters, this will be how you first encounter the Viper King, and regardless of whether you have it on or off the later Alien Rulers work this way in general.


The final possibility is exclusive to playing War of the Chosen: in that case, you can turn on 'integrated DLC'. This will make it so that each Alien Ruler will be assigned to one of the Avatar Project Facilities, as Facilities become available and the previous force level rule allows them to enter rotation. The game will actually tell you that a 'particularly powerful alien' is at a given Facility, both when the initial assignment happens (Amusingly, if they enter rotation with no Facilities to be assigned to, you'll get this announcement before the Facility they're attaching to gets announced, once the Facility spawns) and anytime you look at the facility, including when you're considering launching a mission there. It won't tell you which Alien Ruler it is, but it's easy to work it out on your own since they'll be assigned in the order they're allowed to enter rotation; whichever facility gets assigned first is the Viper King, second is the Berserker Queen, and third is the Archon King. The Alien Ruler will then sit tight on that facility indefinitely; once you've hit their facility, however, if they successfully escape they'll switch to the normal rule of showing up on any ol' random mission, including the usual rule of getting one mission's grace period for sure and so on.

On this note, the game is nice and won't let Chosen spawn into a mission that has an Alien Ruler skulking about. More precisely, an Alien Ruler having ever been in the mission ensures that the Chosen will never spawn into the mission. I'm not entirely sure how this interacts with plot-missions forcing Chosen fights, in terms of which one gets 'priority' or if those missions are just plain exceptions in which both can appear. (I've never seen an Alien Ruler in a plot mission whose Chosen I haven't already permanently killed, but this doesn't necessarily mean anything) I'm similarly not entirely sure whether Alien Rulers are forbidden from showing up in the first part of Chosen Strongholds: I'd expect them to be forbidden from popping into those, but it's difficult to cleanly test it, so I'm not 100% sure. Outside those possible edge cases, though, a mission has a Chosen or an Alien Ruler, with the Alien Ruler getting priority. And to be clear, I do know that the 'Alien Ruler guarding a Facility' setup gives the Alien Rulers priority: if a Chosen should be jumping you when you hit such a Facility, their appearance will be deferred to the next acceptable mission, no possibility of them displacing the Alien Ruler. (Which is part of why I'm not sure what happens with plot missions)

Surprisingly, the game is perfectly happy to have Alien Rulers 'overlap' even if you don't have Integrated DLC on. That is, it's possible to encounter the Berserker Queen, then have the Archon King pop in a few missions later even though you haven't finished up with the Berserker Queen. It won't normally happen, as the Alien Rulers are spaced far enough apart in Force Level that you'll usually be done with the Viper King before the Berserker Queen shows up and done with her before the Archon King hits the field, but if nothing else turning on the Nest and then taking forever to actually hit it can mess up their pacing. (And this is perfectly plausible to happen organically in a Legend War of the Chosen run, in fact, assuming you turned on the Nest)

It's such a rare situation I'm not entirely sure how the mechanics actually work, in terms of stuff like the mission gap between Alien Ruler appearances. I suspect each Alien Ruler has a separate 'clock', from my limited experience with this situation, but if someone code-dived and told me there's just one global clock for Alien Rulers and the game randomly selects from all Alien Rulers in the active pool once it's time for one to appear? I'd find that perfectly plausible.

Anyway, a more subtle point about Alien Ruler mission appearances: the Shadow Chamber will never forewarn you of them! It will mention their podmates if they brought any, but since they don't in their first encounter it's entirely possible to have the Shadow Chamber tell you that there's 9 enemies, be paying enough attention to know when you've killed 9 enemies, and surprise there's an Alien Ruler hanging out at the evac point! This is a little less important if you're playing with War of the Chosen's DLC integration option, since they can't jump you anywhere at any time until after you've deliberately activated them as individuals and so surprise encounters will always have the podmates mentioned if you've got the Shadow Chamber, but if you're not playing with that option it can be quite the nasty surprise. (And even with DLC Integration, it's not like the Shadow Chamber mentioning Vipers is automatically a clear sign the Viper King is present) So if you're not playing with DLC integration, you should basically paranoidly assume any mission can have an Alien Ruler, in terms of playing cautiously. Though obviously this comes with the caveat that, in War of the Chosen, if one of the Chosen teleports in there's no Alien Ruler to worry about, so you can reduce your paranoia in that case.

That said, it's worth pointing out that the Alien Ruler replaces a pod that would otherwise have spawned, so if you have a good sense of what is the normal range of enemy counts for your point in the game, you can still often tell an Alien Ruler is going to jump you by virtue of a depressed enemy count being predicted. 6 enemies being predicted by the Shadow Chamber is a particularly extreme example, as generally by the time the Shadow Chamber is up 6 enemies is too few to be possible without a pod being 'secretly' replaced.

Moving to the tactical layer, another quality that's unusual about Alien Rulers is their in-mission spawn location preferences: as I noted in the Sectopod post, Alien Rulers use the 'boss' spawn routine, which is to say that in the majority of missions the Alien Ruler will be one of the last pods you fight, all the way back near the objective, often actively guarding/attacking it. (In 'defend the device' missions you can get forewarning of the Alien Ruler's presence by virtue of seeing them attack the device)

Of course, in Retaliation missions -the kind the base game uses, not the kind War of the Chosen adds- that rule of thumb gets thrown out the window, with it perfectly plausible to stumble into the Berserker Queen on literally your first move. This is one of the few reasons I think Phantom and Conceal have any utility in the base game, because being able to search for your first pod without starting Ruler Reactions can be the difference between a good mission vs a failed mission with every squad member injured or dead. The Berserker Queen, in particular, will usually first jump you in a Retaliation mission if you're playing below Legend. (And aren't running Integrated DLC... which is exclusive to War of the Chosen)

To be honest, I'm not a fan of Alien Rulers hijacking the 'boss' spawn routine. The Alien Rulers are already a rough fight, where they tend to eat up all the squad's attention and demand you expend limited resources to get through: the game endeavoring to have them be the last fight actively encourages a 'But what if I need that Elixir later?' attitude until they're all dead. This is particularly egregious with the Frost Bomb, Hunter's Axe Throw Axe special, and to a lesser extent Shadowfall on the Shadowkeeper, in that optimal play involves hoarding your shiny-cool capabilities instead of using them because they're so important for fighting Alien Rulers. (This is one reason why Integrated DLC is a huge improvement in my opinion: you can freely use Cool Toys up in regular missions until you've actually hit a given Alien Ruler's Facility, and then can stop hoarding once that particular Alien Ruler is dead)

But even with stuff like regular Frag Grenades, it's a conspicuous problem. Your first encounter with the Viper King is going to be a lot rougher if you used up all your Frag Grenades and so can't immediately, reliably shave off its Armor. Your first encounter with the Berserker Queen is going to be a lot easier if you held onto your lucky Gas Grenade so you can Poison her. Etc.

Also, it should be noted here that Integrated DLC uses a different spawn routine for that first encounter at an Avatar Project Facility. I don't understand exactly how it works, but most often the Alien Ruler will spawn outside but close to the building itself, and then attempt to patrol around the building in that same range. (ie they generally won't patrol away from the building, nor inside or atop it) Sometimes they'll just patrol back and forth just in front of the building instead, other times they'll patrol back and forth just behind the building... but 'patrol around the entire building' seems to be what the game is shooting for. It's not remotely perfect -which is part of why I don't understand the exact details- as I've occasionally seen eg the Archon King just hanging indoors, just on the other side of a door, refusing to move until he hears combat noises nearby at which point he patrols out through the door and activates because he's found my non-Concealed soldiers.

In any event, I personally strongly recommend, if you have Integrated DLC on, that you endeavor to always bring a Reaper into Alien-Ruler-guarded Avatar Project Facilities, and try to find and Overwatch ambush the Alien Ruler if at all possible. You'll want a Reaper because the spawn routine is extremely consistent about having a regular pod patrolling, placed so it's the default first encounter, and only a Reaper can reliably sneak around, keeping an eye on pods, without ever becoming trapped by them patrolling so close their detection radius is atop your soldiers. With a Reaper present you can have the rest of the squad skirt around such pods by a much larger radius, so there's no chance of becoming trapped: it's possible to sneak to an Alien Ruler without bothering with a Reaper, but it's much harder and requires a certain amount of luck outright.

If you think that all sounds like a huge pain, I'd still recommend bringing a Reaper. Blowing your Overwatch ambush per se on the Alien Ruler is optimal, but the key thing here is arranging to find the Alien Ruler without activating it. Even without squad Concealment, just arranging for the Alien Ruler to patrol into a bunch of Overwatch fire will (usually) do a lot to make it an easier fight, and a Reaper will make it a lot easier to set that up.

Final spawn note: every Alien Ruler has a designated tagalong species in their pod. They consistently have no tagalongs the first time they show up, then have one tagalong the next time they show up, and then two the third time they show up. I've no idea if Legend allows them to go even further; I doubt it, given normally pod sizes cap out at 3, but it's not something I've tested or confirmed through code-diving or anything.

The Alien Rulers are easy to identify when they show up. Even aside Bradford and Tygan nattering at you about how they're Vahlen's escaped experiments once you spot them, Alien Rulers have a special icon in your target list and next to their HP meter;

as well as having their HP meter blocks in a unique green color. These qualities are unique to them, even into War of the Chosen. (The Chosen have their own icon and HP meter color)

On a different tactical note, Alien Rulers are one of a handful of enemies to not perform standard fallback behavior. (ie they won't run off to an inactive pod, de-activate, and join said pod) Instead, when an Alien Ruler hits one of its previously-covered triggers for deciding to run, it spends a turn summoning a 'psionic rift' at a random location within a single action point of movement of its current location. The next time they have an opportunity to act, they will immediately run to the portal: this is actually a real movement action, triggering Overwatch, possible to interrupt by killing them, and indeed if you catch them with Overwatch fire from the Bolt Caster it can Stun them to interrupt it. (I assume a Bladestorm/Retribution could also interrupt with a Stun, though it hasn't happened in my own play) There's even an Achievement for killing an Alien Ruler as it's attempting to escape.

Of course, if the Alien Ruler touches the portal, it immediately vanishes from the field and you're going to have to wait until a later mission to kill it.

An annoying quirk of a successful Alien Ruler escape is that in some sense the game considers the Alien Ruler to be alive, active, and visible: the combat music will never change until you complete the mission or a special external trigger (ie a plot mission cinematic) overrules the current tune (Which is what happens if you have pods active completely continuously throughout a mission), and a key bit of behavior won't function correctly: normally, if no enemies are alive on the map, ending your turn will fail to pop up the 'alien activity' UI element, but an Alien Ruler escaping will cause this effect to persist forever. This is especially problematic on timed missions, especially if you aren't aware that Alien Rulers are usually the last pod, as it's easy to end up moving cautiously on the idea there must be another pod left and whoops you end up moving so slow somebody gets left behind totally unnecessarily.

This combines in a particularly nasty way with another tactical quality all Alien Rulers share: they each have an attack that very reliably inflict instant Unconsciousness. In most missions, that's unpleasant enough since Unconsciousness is basically being dead from a tactical perspective, and indeed the biggest part of why I default so heavily to Revival Protocol on Specialists over Haywire Protocol is so I can fix Unconsciousness when an Alien Ruler inflicts it. But in a timed evac mission it's so much worse, since you'll actually be down at least a third of your squad due to needing someone to cart the Unconscious soldier to the evac point if you either don't have Revival Protocol or whoops your only soldier with it is the one who went down. This is especially awful in Neutralize VIP missions, where you're normally committing another soldier to carrying the VIP's body (Psi Operatives can actually Dominate the VIP and have them walk to the evac point, and that actually works, but you might not have the option yet even if you consistently pursue Psionics in your runs), and so an Alien Ruler knocking somebody Unconscious can easily lead to you having half your squad out of the fight.

Especially since Neutralize VIP missions have reinforcements triggered by KOing or killing the VIP, so even if you deal with the Alien Ruler before handling the VIP (Plausible), you're still going to need to do more fighting.

This is all awful enough that it's genuinely worth trying to manipulate mission timing so the Alien Rulers don't jump you during a Resistance-request mission, if you're able to keep track of all the relevant information. (Or are willing to savescum, I guess) Stuff like putting off hitting an Avatar Project Facility until you're confident the Alien Ruler has to jump you, and then hitting it so they spawn there instead of in a timed mission.

Integrated DLC substantially sidesteps these issues, thankfully, but even with it on you may wish to time your initial hit on their Avatar Project Facility so they're unlikely to have their second appearance in a Resistance-request mission, if Fatigue considerations allow you to do so. eg if no Retaliation mission is imminent (Which you can manually check in the Dark Events screen), and you've just completed the month's Guerrilla Op, usually the very next mission is going to be a Resistance mission and so hitting the Avatar Project Facility at that point can't have them promptly jump you in the following Resistance mission due to the minimum 1-mission delay.

Anyway, all Alien Rulers also share a brand-new tactical mechanic...

... Ruler Reactions.

Broadly speaking, this can be summarized as 'anytime one of your units acts, the Alien Ruler immediately gets a turn in the middle of your turn'. This summary misses out on a lot of important points, though, not the least of which is that War of the Chosen makes several important changes to Alien Ruler turn mechanics.

So first of all, that 8-14 turns before an Alien Ruler bails I mentioned earlier? Ruler Reactions advance that clock, and indeed are normally going to be the primary advancer of it. In normal play, you're probably going to have an Alien Ruler gone in less than 2 regular turns, whether by killing it, knocking its HP low enough to trigger its retreat behavior, or triggering so many Ruler Reactions they decide it's time to leave.

Second, Ruler Reaction turns only get 1 action point. This has several important implications, not the least of which is that Stun effects have a greater impact than you might intuitively expect since the amount of Stun you inflict is the action points negated: a Stun of 2 will negate 1 full turn on most enemies, but negate 2 full Ruler Reactions. Even aside Stun, though, this means Alien Rulers can't move to a better position and then separately perform a ranged attack from one Ruler Reaction.

Third, Ruler Reactions advance the Alien Ruler's personal 'clock' like a proper turn for most purposes, which is to say that if you inflict 3 turns of Burn on an Alien Ruler and then provoke a bunch of Ruler Reactions they'll take damage three times and then be clear of the Burn. The only exception is Stasis, which suppresses the Ruler Reaction mechanic entirely, and of course then terminates under normal turn 'clock' rules. (Stasis makes Alien Rulers a lot easier: if you play the game a lot without owning Alien Hunters and come to disdain Psi Operatives, then buy Alien Hunters, you should give Psi Operatives a second chance)

Fourth, if an action doesn't expend action points, this always means it won't provoke a Ruler Reaction. (At least, I haven't discovered an exception) Surprisingly this includes conditional modifiers: a Hair Trigger refunding action points will prevent that particular shot from triggering a Ruler Reaction, Serial or Reaper-the-skill-backed kills won't trigger Ruler Reactions either, and mercifully this extends to successfully Headshotting Lost not triggering Ruler Reactions. (It would be a horrible nightmare if clearing out Lost wasn't exempt...) Note that this includes the Distraction Hacking reward, which refunds your entire squad's action points: if you find yourself in a position of being guaranteed to succeed at Distraction, it's absolutely worth performing that Hack if an Alien Ruler is active and your squad is getting low on action points.

Fifth, Concealment protects against Ruler Reactions. Note that an action that breaks Concealment will trigger a Ruler Reaction (Unless the Alien Ruler was inactive prior to breaking Concealment!), and in War of the Chosen Shadow risking breaking will provoke a Ruler Reaction even if Shadow didn't actually break. (ie you're free to toss Claymores, shoot Claymores, or use Sting) To be clear, Silent Killer is no protection: a regular shot will trigger a Ruler Reaction, even if it was guaranteed to hit, guaranteed to kill, and resultantly had a 0% chance of breaking Shadow. The Shadow gauge appearing always means that particular action will trigger a Ruler Reaction.

Sixth, Overwatch Fire doesn't trigger Ruler Reactions. Entering Overwatch will provoke Ruler Reactions, but reaction fire occurring is safe. One quirky implication of this is that the Berserker Queen and Archon King are, uniquely, enemies that don't use Cover but are worth setting up an Overwatch ambush on.

Seventh, note that once-per-turn reactions like Bladestorm do not 'reset' with Ruler Reactions: if you have a Bldestorm Ranger use the Katana to Slash an Alien Ruler and then trigger a bunch of Ruler Reactions, what will happen is the Ranger will Slash, Bladestorm in response to the Ruler Reaction the Slash provoked, and that's it, you're done Bladestorming until you actually end your turn.

Then there's those differences between the base game and War of the Chosen I alluded to.

Broadly speaking, it's straightforward enough to say War of the Chosen made Ruler Reactions less general. As for specifics...

First of all, line of sight: in the base game, if an Alien Ruler is active and any enemy can see a given soldier acting, that action will trigger a Ruler Reaction if it isn't one of the previously-mentioned exceptions. In War of the Chosen, the Alien Ruler must personally witness the soldier acting to Ruler React, though note that even a brief glimpse of part of the action counts: a Ranger who Slashed an enemy, with this starting and ending outside the Alien Ruler's sight, would still trigger a Ruler Reaction if the Ranger passed through the Alien Ruler's vision for even a single tile. Similarly, if the action directly destroys terrain such that the Alien Ruler can now see the soldier, this will provoke a Ruler Reaction even though the soldier was never seen acting by the Alien Ruler: be careful when taking inaccurate shots or using terrain-wrecking tools like grenades.

This is a huge difference. In the base game, an Alien Ruler stumbling into an ongoing fight forces you to immediately divert your entire squad's attention to the Alien Ruler, even if the Alien Ruler can only see one squad member. Only Squadsight actions might let you act on enemies without provoking Ruler Reactions. In War of the Chosen, a more spread-out fight can result in you getting the opportunity to clean up stragglers before focusing on the Alien Ruler properly, instead of basically having to leave multiple hostiles alive and in a position to torment your squad.

Second, in the base game any action that harms an Alien Ruler will provoke a Ruler Reaction, even if no enemy could see the acting soldier. ie having Sharpshooters snipe Alien Rulers, Specialists use Combat Protocol from beyond line of sight, Grenadiers lob grenades from behind large trucks, and so on, will all provoke Ruler Reactions if the Alien Ruler is hurt by them. (It very specifically requires harm occur: a Sharpshooter missing an Alien Ruler at Squadsight ranges is fine, so long as no other enemy had sight on them when they fired) They're not very smart about using their Ruler Reactions if they can't see anyone, as they'll just wander randomly instead of moving to where the damage came from the way you'd expect, but this does mean it's mildly risky to have a Ranger spot for a Sharpshooter while Concealed: the Alien Ruler may stumble into revealing the Ranger.

War of the Chosen removing this qualifier is... very exploitable, unfortunately. There's the obvious point of it letting you do lots of safe, 'free' damage under the right conditions, but less obvious is that it lets you cheese their escape mechanics. In the base game, successfully arranging to snipe an Alien Ruler is helpful, but they'll inevitably run away if they weren't already quite low on health, limiting how effective such a tactic is. In War of the Chosen, if you're under no time pressure from the mission itself and set up a Concealed spotter+Sharpshooter sniping from Squadsight ranges, you can take any Alien Ruler from full to dead with zero risk. (Aside the possibility of another pod patrolling into your squad and messing this up, but that may well be irrelevant; maybe you've killed everything else on the map, for example) Admittedly, that could be viewed as a positive if you just really hate fighting Alien Rulers and would rather cheese them...

Third is the consideration of a normal turn. In the base game, Alien Rulers get a regular 2-action-point turn during the regular enemy turn, on top of Ruler Reaction turns. In War of the Chosen, they do not get a regular turn. Caveat: I've had Alien Rulers get full turns at times in War of the Chosen, particularly when I've tried to stall so they don't escape through their portal... but not every time. I'm not sure what the pattern is. It feels like the Archon King is particularly prone to this, but I'm honestly not sure that's a real trend. So avoid making plans that fall apart if the Alien Ruler gets a full turn, just in case.

I don't really get this particular change, and genuinely have to wonder if it's an accident, a side effect of some other change. In any event, I don't like it even aside the glitchy inconsistency of it, as the primary effect it has is to create even more ability to exploit Alien Rulers: if you end up in a situation where you know exactly where they are but they can't see any of your squad -which can easily happen via Target Definition, less easily by using a Concealed soldier to find their exact location after they've ended up out of sight, or everything happening to line up so they moved into a narrow blind spot during a Ruler Reaction- you can do a bunch of free damage in complete safety. Indeed, this is part of why you can just Squadsight Alien Rulers from full to dead so easily in War of the Chosen -even if the base game didn't have out-of-sight damage trigger Ruler Reactions, the Alien Ruler would still get a regular turn to wander around and potentially break the setup.

Fourth, War of the Chosen has made a few action-point-spending abilities exceptions that don't trigger Ruler Reactions. Skulljacking, Skullmining, picking up loot, and most crucially reloading are now safe actions to perform around Alien Rulers. This last point is a substantial boost to the Bolt Caster, making the need to reload between shots much less of a flaw, and more broadly makes Auto-Loaders less important. (A Free Reload never triggers a Ruler Reaction, unlike a regular reload in the base game)

This is actually casually editable via an exposed config file. (XComGameCore, inside the DLC2 folder) If you know the internal name of an ability and want it excluded from Ruler Reactions, you can just edit this file yourself. Maybe you hate how healing soldiers can put you in the hole when fighting Alien Rulers, for example.

The primary reason I mention the file, though, is that you can look in the base-game version of this file and see reloading is in the list of exclusions... but commented out. So apparently they did consider making reloading an exception to Ruler Reactions all the way back in the base game, but changed their minds for... some reason. Even though Ruler Reactions triggering on reloads really hurts the Bolt Caster, where a notable chunk of the Bolt Caster's appeal is its utility against Alien Rulers!

This causes me actual pain to know. Hopefully you now share my pain.

Anyway, fifth, the Lost never trigger Ruler Reactions. Thankfully. It would be really horrifying if they did.

I'm not sure if the Resistance soldiers that help you in the new variation of Retaliation missions are also exceptions. I suspect the answer is yes, given the narrow focus of the mechanics on your soldiers, but it hasn't cropped up in any of my own runs as yet and isn't clearly stated in any of the files I've dug around in, so I don't know for sure.

Ruler Reactions are the element of Alien Ruler design where my feelings are most mixed. On an abstract design level, I think it's a clever solution to resolving one of the problems tactical games often struggle with. Tactical games often want to have powerful boss enemies that can threaten your entire team singlehandedly, and the usual approaches to making such bosses dangerous -such as giving them monstrous statlines- pretty much always have layers of problems that can largely be traced back to the fact that the fundamental combat system is built around groups of units fighting other groups of units. Ruler Reactions is conceptually an elegant way of cutting the Gordian knot, making a boss roughly equivalent to your squad by virtue of getting to act for each member of the squad.

Unfortunately, in actual execution it's a surprisingly awful mechanic, between inherent jank to the idea, some questionable specific decisions to the mechanic, and some more fundamental problems with how it intersects with XCOM 2's broader mechanics.

First of all, the way it intersects with pod activation mechanics is horrible, particularly in the base game where Ruler Reactions are basically guaranteed to trigger off of any soldier acting. The pod activation mechanic has always had issues with mild differences in choices having a bizarrely swingy impact on gameplay, where literally a difference of 1 tile of movement can decide whether an enemy pod wanders into sight and does nothing useful or you pull the pod during your turn and every member gets a full turn to attack your squad, but with an Alien Ruler even pulling a pod with your first move can go horribly wrong if your squad isn't perfectly positioned to immediately and efficiently take on the Alien Ruler.

Exacerbating this first issue is the decision to have Alien Ruler spawn behavior deliberately angle to make them your final encounter in the mission. If the game endeavored to have them be your first encounter, you'd spot them while Concealed and have the opportunity to get into proper position without it triggering a bunch of Ruler Reactions. I get why they didn't do this -it would let you use Overwatch ambushes to do a lot of damage with no Ruler Reactions, rapidly triggering their retreat without really engaging with them as real enemies- but the point is that having them show up last makes it a lot more likely you'll end up pulling the pod without being properly ready for it and have what really ought to be a minor error magnify into a huge problem.

This is all particularly egregious in the base game, as any soldier performing almost any generic action will almost always provoke a Ruler Reaction...

... but War of the Chosen's tweaks, while it's good they significantly reduce the pressure put on the player, have the unfortunate result of making it so the most important thing when fighting Alien Rulers is knowing how to game the Ruler Reaction mechanic, arranging to maximize damage with a minimum of Ruler Reactions triggered via exploiting fiddly details of line of sight, tossing grenades from around corners, etc. Among other points, the order you do things ends up bizarrely important in not-immediately-intuitive ways: having a Specialist heal someone, for example, can be counterproductive if the Alien Ruler can see that Specialist right now, since it will trigger a Ruler Reaction, potentially more than undoing the heal. Thus, a Specialist who is currently out of line of sight can heal safely, but if you trigger a Ruler Reaction first and they move so they can see the Specialist, suddenly this is a bad idea, a distinction that doesn't apply to normal combat.

Part of the problem is the unevenness of action point significance. XCOM 2's default design is that a unit gets one 'productive' action point expenditure per turn, in the sense that moving is only indirectly useful to winning fights and is one of the only default actions that doesn't end the turn. The player moving a soldier to flank and then shooting will trigger two Ruler Reactions, both of which can be spent on 'productive' turn-ending actions: the action economy is thus actually stacked against the player in a fairly significant way. I honestly don't think regular movement should've triggered Ruler Reactions: the action economy of Ruler Reactions would be much closer to parity if pure movement didn't trigger Ruler Reactions.

The game does try to counterbalance things a bit, with the Alien Rulers having AI quirks and mechanical quirks that attempt to prevent them from just spamming turn-ending attacks every Ruler Reaction, but these... don't work very well, though I'll be discussing this topic more when covering the individual Alien Rulers.

Correlated to this action economy issue is that the Ruler Reaction mechanic has the very odd effect that a player has to decide whether a given action is even worth performing. In normal combat, you might decide against a given action as eg a waste of ammo, or inferior to an alternate action the soldier could be performing, but you will almost never have a soldier actually skip their entire turn. With an Alien Ruler about, suddenly stuff like Quickdraw spreading its damage across multiple actions can make it undesirable to take said shots, and any class taking shots with middling accuracy is a very different, much more dangerous gamble than in normal combat.

This is janky in and of itself, but what makes it worse is that it isn't completely displacing regular mission dynamics. This issue is, in a metaphorical vacuum, weird but not bad: fighting a lone Alien Ruler without context is a different experience, but this differentness is arguably appealing if we're willing to ignore points like how some classes suffer badly against Alien Rulers and others hold up fine. However, you still spend most missions under time pressure, where skipping turns outright can fail you the mission even if turn-skipping is strictly optimal for fighting the Alien Ruler, and if there are other enemies about skipping turns gives those enemies more opportunities to act, a lose/lose situation. Notably, past your first encounter Alien Rulers will always have regular escorts, ensuring that if you don't get lucky with Overwatch fire this issue will exist!

Ultimately, the main reason War of the Chosen makes Alien Rulers much more tolerable is that Integrated DLC lets you very reliably substantially bypass the Ruler Reaction mechanic, rather than successfully re-tuning it to be a properly engaging, fair challenge. If you don't run with Integrated DLC, War of the Chosen still has Alien Rulers frustrating, uneven experiences where things that shouldn't be a big deal can get people killed and missions failed, just less often than in the base game.

On the plus side, when War of the Chosen returned to the concept of recurring super-elite bosses, it didn't try to implement a new variation on Ruler Reactions.

On the minus side, I have doubts the XCOM series is liable to ever return to the Ruler Reaction mechanic, even though it's a very solid core idea and could have been tuned much closer to fair just by doing things like not making regular movement trigger Ruler Reactions. Fundamental mechanics changes could also help a lot, by which I mean that Chimera Squad does away entirely with pod activation as a mechanic and so could've implemented something like this without running right into one of the worst problems... but Chimera Squad didn't try to bring back Ruler Reactions, as a concrete illustration of 'XCOM is probably never touching this mechanic again, not even if Firaxis makes a game it would fit into perfectly'.

Alas.

Returning to more hard mechanics commentary, it's worth pointing out the Alien Rulers have a couple AI restrictions that have important implications in connection to the Ruler Reaction system.

The first of these is that Alien Rulers hate attacking soldiers who are currently debilitated. (Suffering from any negative status effect whatsoever) Strictly speaking, this is actually a broad AI rule of thumb, but most enemies give relatively little weight to this, where eg a Stunned soldier in the open will be shot at over a healthy soldier in Cover. Alien Rulers give a lot more weight to it, where if their options are 'attack an afflicted soldier' and 'perform no useful offensive action', they'll usually ignore the afflicted soldier, preferring to advance on the rest of your squad or the like. I'll be going into the exact implications a bit more with individual Alien Rulers, but it's something to keep in mind broadly.

Second, Alien Rulers are coded to heavily prefer to spread their attacks around. Again, this is actually a general AI truism, but one that for most enemies is easily overruled by other factors, where eg a soldier flanked by multiple enemies is probably going to be shot by all of them if none of your other soldiers is exposed... whereas Alien Rulers will often do stuff like attack one soldier, then on their next Ruler Reaction notice that particular soldier is the only person they can currently attack... and still refuse to attack them.

On the plus side, this means it's actually pretty rare for them to kill one of your troops, since they won't usually pile damage onto one target. On the minus side, this means they tend to screw up a sizable fraction of your team if you don't successfully drive off or kill them basically instantly. This is especially painful in hard timer missions, where messing up the entire squad may have more dire consequences than having one soldier go down. (eg the entire squad is lost because nobody makes it to the Evac point in time)

These bits of AI behavior also connect in an interesting way to my suspicions that the Alien Rulers were originally meant to be more Predator-esque figures, as the resulting highly sub-optimal behavior is... actually very much in line with what I'd expect an overconfident sport-hunting monster to do, in terms of being a fighting style that attempts to show off one's superiority over the enemy instead of, you know, killing them dead.

It's one of the lightest bits of evidence pointing toward the 'Alien Rulers were supposed to be Predator figures' theory, since the behavior in question is regular AI behavior and is yet another example of the game doing behind-the-scenes stuff to make the game easier on you: I wouldn't be at all surprised if the devs never actually thought about these AI routines in terms of in-game representations of personality and just did it to make Ruler Reactions less overwhelming of a mechanic.

But it's not inconsistent with the theory, either.

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With these broad points out of the way, next time we'll be covering the first of the Alien Rulers: the Viper King.

See you then.