Zombie gameplay comes to XCOM 2 with War of the Chosen, the expansion launching next month on PlayStation 4, Windows PC and Xbox One. Here, Firaxis offers a look at the first mission within a mode so big the game's creative director said it could have become a full-on sequel.

In War of the Chosen, the player will make and manage alliances with three Earth-based factions. In the video above, Firaxis' Garth DeAngelis, XCOM 2's senior producer, explains the setup, in which the player is contacting two mistrustful factions, the Reapers and the Skirmishers.

Both have different means of dealing with the Lost, the zombie-like horde the game will introduce. The Reaper and Skirmisher leaders must be escorted safely to a negotiating point to complete the mission. Fortunately for the player, the Lost do not use cover, nor do they have ranged attacks. But they also spawn at the sound of explosions.

Then there's the Assassin, an agent of the Chosen, the leadership of the occupying authority in XCOM 2's story. Dealing with her will involve keeping your fireteam personnel from being abducted and interrogated.

War of the Chosen comes to XCOM 2 on Aug. 29.