Bungie confirmed the Symbiosis update for Marathon will release on December 8, introducing Expedition, a co-op PvE mode with roguelite elements and randomized upgrades. The update also adds Limbo, a social hub with a firing range and the Bishop Runner Shell, a sword-wielding robot character.
The update includes a beta PvP Deathmatch mode and free play from December 8 to 15. Bungie's plan to improve core mechanics and player agency beyond competitive play follows the shift from Marathon's initial PvP focus.