War of the Chosen was announced at the Electronic Entertainment Expo 2017. One of them, the Templars, notice the glow coming from the sea and points out that a new conflict will soon begin. After the Elders are defeated, a new cutscene after the original ending shows the three new factions emerging from the shadows. The final mission also remains the same, except that each Chosen who was not killed permanently will appear to fight the Commander's avatar and his forces. Should XCOM successfully locate and destroy a Chosen's stronghold, they are destroyed permanently. Despite being killed in battle, each Chosen is revived and returns to attack on a later occasion. As the game progresses, XCOM is occasionally attacked by the Chosen, three elite alien warriors with orders from the Elders to recapture the commander.

One of them introduces three factions who also oppose the alien occupation the Spokesman orders the commander to join forces with them to bolster the resistance's efforts. The plot remains mostly unchanged from the original game except from a few cutscenes. Six of the voice actors new in the expansion are known for their roles on Star Trek: The Next Generation: Denise Crosby, John de Lancie, Jonathan Frakes, Michael Dorn, Dwight Schultz, and Marina Sirtis. Other new features include a daily challenge mode, as well as the ability to create posters featuring your custom characters that will appear inside the game world. The expansion also adds a neutrally-aligned zombie-like enemy type called the Lost, former humans created during the invasion that will attack both ADVENT and XCOM in battle, along with new ADVENT units with exclusive abilities. For research, breakthroughs and inspirations are made to increase the speed that researchers work at, sometimes instantly being able to complete a project.

Other new features include a revamped strategic layer and the 'Bond' system, in which pairs of soldiers develop special abilities that are accessible when both are deployed during a mission, however, when a bonded soldier is killed, their partner may temporarily enter a 'berserk mode', ignoring any player orders and attacking targets at random, or they may panic, becoming uncontrollable and fleeing from battle.

Each faction also provides covert ops missions in which soldiers can be deployed to obtain extra resources, delay the Avatar project, or gather info about the Chosen's strongholds, as well as other benefits. The game also introduces three rebel factions that antagonize each other, but grant special hero classes once their allegiance is earned the Reapers, specialized in sniping and stealth, the Templars, who employ unique psionic abilities, and the Skirmishers, former ADVENT soldiers with exclusive equipment and tactics. The Chosen continue to appear occasionally during missions even after being defeated, and can only be killed for good once their base is destroyed as well. As the game progresses, the Chosen gain new exclusive abilities over time, and eventually become able to launch a direct attack on the Avenger. The expansion introduces a new set of enemy aliens called the Chosen, three elite alien-human hybrid warriors tasked by the Elders to defeat XCOM and recapture the Commander The Assassin, who relies on stealth and melee attacks the Hunter, that uses a long range rifle that fires bullets that track their targets and the Warlock, who uses psionic powers and can take control of several of the player's units at once. The War of the Chosen expansion makes changes to XCOM 2 's campaign structure and adds new enemies, story elements, new hero characters, modifiers, and more behaviors for characters. A defense team known as XCOM must repel and resist an alien invasion. XCOM 2 is a turn-based tactics video game.

Xcom 2 war of the chosen spark