XCOM: Enemy Within escalates the alien invasion, introducing body modification, sky-squids and Mechtoids. After seeing the initial reveal at Gamescom, I was eager to try the expansion before release, but when I had the chance last week, I hadn’t expected to see humanity turning on itself. XCOM have encountered a new threat and this one originates much closer to home.

The first time one of my agents shot a human, bright red blood spraying from the wound, I was slightly taken aback. Despite the build-up to the mission – which told of a paramilitary group disrupting XCOM operations – I still half-expected to find something reptilian lurking just beneath the surface of the skin.

It was not to be. The Enemy Within does not just allow for genetic and cybernetic tinkering with XCOM agents, it also introduces an entirely new threat in the form of Exalt, an elusive army of transhumanist terrorists who are determined to use the confusion of the alien invasion to pursue their own agenda. From the player’s perspective, this adds another layer of activity to the Geoscape, new enemy types and a wider variety of missions.

Exalt don’t attack XCOM head-on. In fact, it’s possible to leave them to their own devices and concentrate on the more pressing matter of repelling the aliens. The problem with that approach is that Exalt are using their devices to hack into XCOM’s systems, stealing money and stalling research, and when they set up a cell in a region, they disseminate propaganda, raising terror levels and turning public opinion against XCOM.

“XCOM are rubbish”, I imagine they bark through their megaphones and type into their spam emails, “remember that time aliens attacked London and a Skyranger arrived with three rookies on board who started crying as soon as they saw a Chrysalid? Or the day your children were abducted by sectoids while a man wearing bits of alien as armour fired a rocket into a nearby dustbin and killed himself?” Even the most loyal of XCOM supporters may well remember such incidents with a frown. Let’s face it, in our efforts to save the world, we’ve all made mistakes.

Over time, Exalt create cells across the world. The more they have, the more damage they are capable of inflicting. To discover them, reconnaissance points must be spent, allowing XCOM to scan the globe in order to intercept transmissions. When a cell is discovered, it remains in view for a few in-game weeks, exposed and ineffective until Exalt manage to relocate it elsewhere. While the cell is in this vulnerable state, it can be taken out of action entirely and that’s when the new mission types come into play.

XCOM don’t bombard Exalt from a distance or attack them with an assault squad. The ultimate goal is to find the base of operations, rather than chipping away at the outposts, so a covert operative is selected to infiltrate and to gather information. This can be any soldier except a heavy or a mech, and some will be more suited to the task than others. No armour can be equipped during infiltration and no weapon larger than a pistol can be carried while undercover, which makes the agent extremely vulnerable during extraction.

Extraction is the tactical part of the mission. After a few days have passed, the infiltrator calls for an extraction team and they are selected, equipped and sent in as they would be to any other mission. On the ground, they’ll be on the opposite side of the map, separated from their undercover colleague, and will be responsible for clearing a path back to the Skyranger. To complicate matters, the lone agent must hack into designated terminals, marked on the map, before leaving. Without the data they contain, the entire mission is futile. And if that agent dies, everything is lost – all the extraction squad can do is hope to escape in one piece.

Exalt are tough opponents. They have access to the same equipment as XCOM, and grenades and rocket launchers can be seen strapped to their belts and backpacks. I replayed the same map twice, attempting to improve after losing four agents on the first pass. Exalt are smart, using cover intelligently and waiting for XCOM to cluster together before launching area effect attacks. They adapted well to my altered approach on the second run-through. Instead of attacking through the congested centre of the map, I split my forces and sent them creeping around the periphery.

Instead of hunting for my troops, Exalt vanished into the shadows. I thought they were stationary, the game allowing me breathing room that I hadn’t necessarily earned. As I blundered onward, moving from cover to cover and attempting to set up a killzone, I realised my mistake. Exalt had used my apparent hesitancy to concentrate their attentions on my covert operative. As he approached the first terminal, four enemies came into view, converging on his position. With only a pistol to defend himself, he was forced to retreat, increasing the gap between my various units and eventually leading to complete and abject failure.

Whether it’s the setup of the map, with the squad split and objectives scattered, or the improvements to AI, the brief hands-on with the Exalt missions marked them out as highlights. They should become more interesting as the campaign progresses as well. Exalt believe that the aliens’ technology and biology can be harnessed to fulfil their transhumanist dreams. They will begin to use alien weaponry, just as XCOM do, and they will follow XCOM in altering the bodies of their operatives. However, they will tread where XCOM fear to go, pushing their modifications to extremes.

The new enemy can be destroyed, although the aliens continue to be the game’s focus and are the heart of the war. Exalt have a base and by capturing intelligence during covert operations, XCOM gather clues as to where it is located. Through a process of elimination, the player can ‘accuse’ a region of harbouring the base, but if the accusation is false, the results are grave. Should the headquarters be discovered, XCOM have a base invasion to deal with, but as the aggressors rather than the defenders.

As an addition to the game’s strategic layer, there’s a possibility that Enemy Within and Exalt will distract from the campaign rather than adding any real complexity to it. The new mission and enemy types add pleasing variety to the tactical combat that is XCOM’s core, but only a full playthrough will determine how the balance of demands on the Geoscape will alter the flow of a campaign, for better or worse. With the new unit modifications already detailed, I hadn’t expected anything as significant as a new faction in this second reveal and I’m convinced that, if nothing else, Enemy Within will have enough content to make another run through the campaign a worthwhile proposition.

I spoke to lead designer Anand Gupta about Exalt’s motives, the second covert mission type, X-COM: Apocalypse’s factions and simulated city, and how to maintain balance while introducing new systems. That’s coming soon.