The story in the game is written by best-selling Warhammer 40,000 author Graham McNeill and Narrative Designer Ivan Mulkeen who will help develop the different factions in the game. The open world is set on the planet of Arkhona in the late 41st Millennium. The player versus player gameplay of Eternal Crusade takes place on the surface of Arkhona that is open to all players. The player versus environment game modes all are set in instanced areas, below the surface of the planet, but the player will first need to discover entrances to them during open world play to enter.