At the PC Gaming Show creative director Jake Solomon outlined War of the Chosen, a massive expansion for XCOM 2 that adds three nemesis aliens, other resistance organisations, new soldiers, new abilities, new gear, zombies, cities full of zombies and too many other features to fit in one sentence. I spoke to Jake Solomon to learn more, and discovered that almost every aspect of the game has been retouched and expanded upon.

Let's start with the Chosen. The team saw the nemesis system in Shadow of Mordor and wondered how those persistent rivalries would work in the context of an XCOM 2 campaign. The result is three distinct alien heroes that will dog XCOM's efforts in battle and on the campaign map. They can run operations on the strategy layer to disrupt your campaign, and they will even taunt you in the command centre. Solomon felt that the strategy layer was a little cold in XCOM—"this is my fault," he says—so expect loads more chatter. In the ship between missions you'll hear Advent news reports spinning your missions. In the bar aboard the Avenger, if you zoom in there's a radio station playing with its own DJ.

Initially your alien nemeses are hunting 'knowledge', which they can acquire in a few different ways, including kidnapping yours soldiers from the battlefield and imprisoning them (you can break them out later). The more knowledge they gain, the more powerful they become. The Chosen ultimately want to find the Avenger, shoot it down with a huge gun and attack the wreckage to recapture the Commander and destroy the XCOM project. If the Chosen get the upper hand in a campaign you will have to play this mission to save yourself. If you manage to keep the Avenger safe, the Chosen will turn up in the game's final missions to make things especially hard. You're going to want to take at least one of them out.

To track down and kill the Chosen you need the assistance of the three new rebel groups— Templars, Reapers and a rebellious human-alien hybrid faction called the Skirmishers. Each Chosen is being hunted by a corresponding resistance faction. You send soldiers to aid resistance activities to improve your standing with a given resistance faction, unlocking leads on the Chosen along with strategic orders and resistance soldiers for hire.

Solomon likens orders to policies in Civ, you enact them to activate a particular effect on the strategy layer or the battlefield layer. One order reduces the Avatar Project count by one bar per turn. Another pauses the countdown timer in a stealth mission until your squad has been revealed. There are dozens of orders themed to fit their associated resistance faction. You can cosy up to multiple factions at once, but obviously it takes time and resources to do so.

Befriending the Templars, Reapers and Skirmishers gives you access to the best soldiers in the game. Resistance heroes are insane. The hybrid Skirmisher heroes are extremely quick, and can take multiple actions in a turn, for example, and they only get better as they level up and gain ability points to spend on powerful new skills. A low-level Reaper skill gives the hero a chance to remain concealed if they fire from stealth. A high level skill lets a hero fire their entire clip in one go, which is potentially amazing. A top-tier Templar skill lets them absorb corpses from the battlefield to create a clone of themselves. Solomon says it will take a long time to unlock the most powerful abilities, but they will be incredibly destructive.

But what about your normal soldiers? XCOM has its own pool of ability points. Clever tactical moves such as successful flank shots in combat have a chance of generating points. If you build a training facility, you can then spend these points on your standard XCOM-trained soldiers. You have to be careful with them, though. In War of the Chosen soldiers become tired if you use them in multiple successive missions. You can send a tired soldier into battle, but there's a chance they will earn quirky traits. Jake Solomon gave the 'obsessive' trait as an example. If an obsessive soldier's clip is empty there's a chance they will use their first action in a turn to reload—anyone who mashes the reload key constantly in an FPS will sympathise. The system is designed to add more character-forming foibles to your squads, and to encourage you to diversify by benching tired soldiers to develop others.

Perhaps my favourite addition in War of the Chosen is the soldier bonds system. As your soldiers fight alongside one another in battle, pairs will be flagged as 'compatible'. If you nurture this compatibility your squaddies can form bonds that come with battlefield effects. Superfriends can potentially fire simultaneously on targets. If one goes down to panic, the other can run over and remove that status effect (Jake also mentioned new types of panic, but we'll have to wait and see what those are). The expansion also adds covert missions that let you send scientists, engineers and soldiers off to a location for a while to earn resources and help out resistance factions, and bonded soldiers will complete these more quickly. The system makes your soldiers more effective and realises the sort of battlefield dramas XCOM players have been crafting for years. I know what you're thinking, are these soldiers just friends, or something more? "It's up to players to decide what a bond represents" says Jake Solomon, diplomatically.

After all that I feel like I've only learned about a fraction of what the full expansion has to offer. The Chosen and the new resistance factions sound like an interesting challenge to manage, but I'm especially glad to hear about the smaller features—crew bonds, soldier traits, alien banter—that should bring more personality into the game. Firaxis says War of the Chosen is their biggest XCOM expansion yet. It already sounds essential.