Boss Rush is a game mode unlocked by unlocking the Forge shortcut. It is accessed from the elevator room, and costs 3 to use (except for the first time, which is free). Completing Boss Rush unlocks Bracket Key.
In Boss Rush, each floor only contains an entrance, boss rooms, and an exit. Bosses do not have a damage per second cap in Boss Rush. Boss rewards are the same as the main game, including Master Rounds should a boss be killed without taking damage, though refraining from picking up a gun on the floor will not guarantee gun drops from later bosses on the floor. Defeated bosses will not drop during this mode.
|Keep of the Lead Lord|
|Black Powder Mine|
- Only one Master Round can be gained per floor, even if multiple bosses on a single floor are beaten without taking damage.
- The lack of a DPS cap allows for extremely powerful gun/item combinations which may be less noticeable against normal capped bosses.
- Boss Rush is a good way to get the 'Lead God' Achievement and unlock Super Hot Watch.
- Similarly, Boss Rush can also be a good way to beat the Turbo Mode challenge.
- Wall Mimics, Keybullet Kin, Pedestal Mimics and Chance Kin can spawn in Boss Rush.
- If Lord of the Jammed is encountered during Boss Rush, and High Dragun is successfully defeated during the run, you will be able to die during the victory screen, as the game is not paused when Boss Rush is cleared. Only the death cinematic is played underneath the victory screen, it does not count towards your death count total, and does not bring up the death log.
- If you pay the 3 required to enter Boss Rush and then leave the game, you will need to pay it again.
- This bug also occurs if you exit the game after Tinker has just finished constructing the elevator and offers you a free first go.