Bungie has detailed its upcoming Symbiosis update for Marathon, which introduces several significant modes next month. Chief among them is the new permanent PvE mode, which Bungie previously experimented with and promised earlier this year.
Symbiosis is headlined by Expedition, a co-op PvE destination with roguelite elements. Expedition pits teams of players against escalating challenges and offers randomized upgrades called Flash Boosts to increase their odds of success.
The Perimeter zone has also been expanded with the new Burrows and Reservoir areas. Another addition is Limbo, a new social hub for players to gather that features a firing range. You can also try out the new sword-wielding Bishop Runner Shell alongside new weapons and gear, such as the Maverick pistol, throwing knife, hack grenade, and V17 flamethrower. Lastly, you can test your skills against other players in the beta PvP Deathmatch mode.
Symbiosis arrives in Marathon on December 8. An open play week will kick off the same day, allowing new players to experience all of Marathon’s content for free until December 15.
The Symbiosis update marks Marathon’s evolution into a more co-op-friendly, PvE experience as its initial focus on PvP extraction has struggled to sustain a substantial audience since its March 5 launch. Bungie announced in September that it plans to spend the rest of 2026 improving Marathon’s core mechanics and features while giving players more agency for how they engage with it beyond competitive PvP.
For more on Marathon, check out our review.
