XCOM Alien Design

I’ve mentioned in a previous article that XCOM: Enemy Unknown’s basic mechanics are, with a few exceptions, easily transferable to the tabletop and would be a significant improvement over D&D mechanics for just about any edition you care to name. Today I’m going to talk about something else tabletop RPGs can learn from XCOM, although this time it’s going to be less of something where you can copy and paste the existing XCOM material in with only minimal changes and more something where a general design philosophy should be learned from, even though the specific implementation cannot reasonably be copied. Today, I’m going to talk about NPCs.

In XC:EU there is a steadily escalating stock of enemy aliens, with new aliens introduced each month. XCOM also gets new funding each month depending on performance so far, and research into alien technology to be replicated and construction of new facilities also takes time (and money, the accumulation of which takes time), so there is a constant arms race between XCOM and the aliens. Here we already see how the direct analogue to D&D breaks down. You could set up a specific campaign whose premise was an XCOM style arms race where the party is under pressure to level or gear up in response to escalating monster threat (I might actually do that sometime), but that’s a specific campaign premise, not something you can generalize to all of D&D.

That said, the way in which aliens become steadily more deadly as time goes on does map to NPCs getting stronger as level goes up. Rather than an arms race where players must level their characters fast enough to keep up with the NPCs, in most D&D games either the NPCs automatically level to match the players or else their levels are static and the players are expected to seek out encounters appropriate to their level.

What can and should be learned from XC:EU’s enemy design is the way the game changes as the power level goes up. As an example, let’s look at a series of three enemies, all from the base game, the sectoid, the muton, and the sectopod. These three enemies are your main bruiser enemy at tiers one, two, and three of the game respectively. You fight sectoids at the very beginning with regular body armor and mundane assault rifles, you fight mutons with carapace armor and laser rifles, and you fight sectopods with titan armor and plasma rifles. Or maybe you fall behind the gear curve and get murdered horribly. What’s important is that, although the sectoid has three health, the muton has eight, and the sectopod has a staggering twenty-five, that is not the beginning and the end of the differences between them.

Each of these aliens has unique abilities that set it apart from the others, even the sectoid, which is going above and beyond the call of duty, since having the basic enemy just move and attack would’ve been fine. The sectoid has a unique power, though. It can mindlink itself to another sectoid, giving the target sectoid an accuracy bonus and an extra hit point. However, if the source of the mind link is killed, the sectoid it’s mind linked to will automatically die. This power is such a double edged sword that it’s actually usually to the sectoids’ detriment to use. Sure, one guy gets an accuracy bonus and the source of the mind link is smart enough to hang back and let the slightly beefier, slightly deadlier sectoid be the meat shield, but he used an action establishing the mind link, he’ll have to reuse an action to re-establish it next turn, and if XCOM gets a clean shot on him, that’s two sectoids dead with one attack.

The muton’s special powers are much more frightening. Unlike the sectoid’s mind link, which is actually detrimental to them if you learn how to exploit it, the mutons’ special power buffs itself and all nearby mutons with both extra aim, extra movement, and extra will (which helps them resist panic when their mates start dying as well as psionic attacks, although generally speaking by the time XCOM has psionic soldiers, it also has the plasma firepower to melt standard mutons with little trouble). They also have a passive ability that causes them to panic nearby units when wounded if those units fail a will save. Finally, they get upgraded with a grenade sometime after their initial deployment, which badly punishes clustering units together. Whereas fighting sectoids is about lining up a shot on the guy in the back to kill him and his frontline buddy with a single hit, fighting mutons is about keeping your distance to avoid being panicked when they get wounded, staying spread out to avoid grenade damage, and putting them down quick so that the action cost of their buff outweighs the movement and accuracy bonuses it grants.

Muton elites also show up at the end of the game, though as bodyguards for enemy commanders rather than as standard infantry. They lack the buff skills of the regular mutons, but can still benefit from them, so the obvious thing to do would be to have a muton elite leading a pair of standard mutons to benefit from the buff, but this doesn’t happen. Instead, muton elites have the power to launch grenades long distances, meaning that they can punish clustering even at range. Muton elites aren’t generally a nuisance by themselves, however (although God help you if, for some reason, you encounter one while you still have tier two equipment), and are more deadly because their high health requires multiple attacks to chew through, their high damage means they cannot be ignored, and they’re encountered bodyguarding the much nastier ethereal units. The tactical puzzle they present is less about killing the muton elites themselves and more about whether or not you think the pure HP damage dealt by the elites will be more or less threatening than the suite of psionic powers the ethereal can unleash on you.

The last of the primary infantry units (and actually more like a tank), the sectopod is a monster not just because of its massive health bar and damage but because of its cluster bomb ability allowing it to hit all XCOM agents in a very wide radius. It also deploys with a pair of hovering drones that can use their action to repair it, necessitating XCOM take the drones out before focusing on the sectopod itself. The massive sectopod cannot take cover, instead relying on its enormous health bar and nigh-immunity to critical hits to avoid damage. As it is a giant stompy robot, it is also flat-out immune to the psionic tricks XCOM is usually picking up around the time it deploys. Its weapons chew through cover in a hurry as well, necessitating XCOM keep moving, which chews up valuable actions in the end game when many classes of XCOM agent can attack twice in one turn – provided they don’t have to rush to new cover first. Making matters worse, sectopods get a free overwatch with a secondary weapon whenever they fire their main weapon, which means when an XCOM agent runs for new cover, they’ll take a shot that does only a bit less damage than the main cannon.

We can also talk about mechtoids, power-armored sectoids that appear a little after mutons and well before sectopods in the Enemy Within expansion. These are also a heavy infantry unit, and deploy with one or two plain old sectoids, however, when the sectoids use their mind link on a mechtoid, it creates a shield around them, giving them a significant health boost. Unlike the drones, who repair damage to the sectopod, the sectoid mind shield can be applied before the mechtoid has even engaged XCOM, can be maintained from very long distances (even though it has to be nearby to activate in the first place), and disappears when the sectoid is killed. Attacking a sectopod before destroying its attendant drones is generally only a valid strategy if you’re confident you have the sheer firepower to focus fire it down before it can receive healing, but breaking through a mechtoid shield rather than running past it to kill the sectoid maintaining it is much more often a solid strategy, both because the comparatively low twenty health and lack of monstrous damage resistance of the mechtoid make it easier for a squad to take out with focused fire, and also because the sectoid maintaining the shield could be 20+ squares away by the time you reach it.

This is all just an examination of the differences between different units who all fulfill the same fundamental purpose of being able to deal and receive large amounts of damage, often with some kind of area attack as the game goes on. Every single tier of the game has other units with much greater differentiation than these basics. At tier one, thin men are highly accurate and can poison your units, forcing you to decide whether you’re going to burn a medkit to heal them even when they haven’t taken much damage or try to finish the mission before their health is sapped away completely (all DoT effects mysteriously end when the mission is successful, which is weird, but mechanically interesting). Floaters are highly mobile and can fly upwards to get around cover with just a few squares of movement rather than taking a dozen to circle around, and can use a special power to instantly teleport behind your squad, invalidating all cover at once. Seekers turn invisible and, if not immediately mown down by overwatch fire when they reappear, will strangle a unit when they decloak, preventing that unit from taking actions until the seeker is killed while also steadily draining their health. Towards the end of tier one, chryssalids appear, with monstrously high movement scores and the power to attack twice in one round if you’re foolish enough to leave an XCOM agent standing next to them, and the power to turn any unit they kill into a zombie, which a few turns later will explode into another chryssalid.

Tier two has cyberdiscs, muton berserkers, and sectoid commanders (sort of, nitpicking about what tier sectoid commanders fit into would take a while and this post is long enough already), tier three has ethereals and heavy floaters, and aliens from earlier tiers often remain relevant in later tiers in a different role – seekers do so little damage per turn that they’re unlikely to flat-out kill tier two XCOM agents, but they can still decloak during a fight with another squad of aliens and strangle one of your guys to prevent them from joining the battle.

In contrast, how many enemies in D&D are nothing but a bigger and beefier version of something that came before? There’s room in D&D for a giant beatstick whose only job is to provide easy to manage goon squads for another, more interesting enemy. Orcs and ogres and fire giants are, at various levels, perfectly acceptable as backup dancers to evil wizards, ogre mages, and beholders. A GM can only keep track of so much at once, so a goon squad whose only powers are “hit adventurer with club” free up more of a GM’s focus for the crazy powers the other, more interesting NPCs have.

But usually, that more interesting NPC is reserved for the adventure boss. There’s often a lot of visual variety in NPCs along the way, but rarely do they have particularly interesting abilities. Sometimes they have special abilities that aren’t combat relevant (a bullywug can jump really far, talk to frogs, and is good at hiding in swamps – all flavorful and good additions, but despite having three special abilities, when you fight it, it’s just a sack of hit points), sometimes the power is barely relevant (when they down a target, gnolls can move up to 3 squares and make a bite attack as a bonus action – which would be interesting if dropping a PC were something that a gnoll could plausibly be expected to accomplish in the average encounter, but it’s not) and sometimes they just don’t have special abilities at all (ogres and ogrillons are like this). The problem is even worse in earlier editions (4e loved the “power so rarely helpful it may as well not exist” paradigm and most monsters 3e and earlier didn’t even have special powers), so it’s nice to see 5e moving in the right direction on this.