Marathon is set to receive its Mid-Season 2 update next week, introducing Vault Breaker, the shooter's first proper PvE mode, but the roguelite-style mode will only be playable for around two weeks before it disappears. Bungie has framed the addition as experimental, with a full PvE mode reportedly planned for season 3, suggesting Vault Breaker functions more as a limited test than a permanent fixture, much to some players' frustration given the short window to try it out.

In Vault Breaker, players infiltrate the Cryo Archive solo or in a duo or trio, tackling progressively harder vaults across multiple runs and collecting a new currency, Vault Data, to upgrade a sponsored kit or purchase other gear. The mode runs from 21 July, when the update launches, until 4 August. The same update also brings refreshed implant iconography, a new "evolution" prestige system for the Cradle with unlockable runner style shells, and smaller tweaks such as toggleable invisibility for the assassin shell, drone-based player highlighting for the thief, and automatic equipping of sponsored kits.