What to know

  • Bio-Bulkhead is found in the Synthetic Nave in the Dissected Plateau region of Fadefields during the main quest One Fell Swoop.
  • After completing One Fell Swoop, Bio-Bulkhead can be farmed via the Big Encore Machine at the boss arena.
  • Key drops include three legendary items: Budget Deity (pistol), Sho Kunai (grenade), Waterfall (grenade).

Encountering Bio-Bulkhead is part of the story in Borderlands 4. Because he’s relatively early in progression, his drop table is valuable for gearing up, and since he becomes farmable later, players wanting these legendaries have repeat exposure. This guide covers exactly what he drops, how to reach him, fight him efficiently, and what loot to expect.

Bio-Bulkhead location: How to reach him

Story Context: Progress through "One Fell Swoop" by allying with Zadra to infiltrate Idolator Sol's Order base and investigate the locust bioweapon project. You'll storm the facility, clear enemies, and use environmental tools (like grappling hooks and locust dispensers) to open armored doors.

Post-Story Farming: After completing the mission, return to Synthetic Nave via fast travel. Head to the boss arena entrance and interact with Moxxi's Big Encore Machine (costs in-game cash, scaling with your level) to respawn the boss for repeated farms.

Route Tip: From the Dissected Plateau fast travel point, follow the main path into the facility, ride the elevator in the central hall, and drop down the chute to the arena. You can skip most enemies on refarms by sprinting.

Press the button on the right

How to defeat Bio-Bulkhead

Bio-Bulkhead is a melee-focused aggressor that charges and jumps constantly, so mobility is key. The arena is a large circular room with two locust canister dispensers (one in the red-lit inner area, one in the blue-lit outer wall). Use your glide pack's dash (Left-Shift on PC or directional + Circle/B on controller) to evade attacks while backpedaling.

Key Mechanics and Attacks:

  • Shield Phases: Starts immune at the beginning and after each health segment. Grab a locust canister with your grappling hook, then throw it at the boss to shatter the shield (creates a vulnerable window).
  • Exposed Armor: Once shielded, target the armor with Corrosive or Cryo weapons for bonus damage. Avoid Shock, Radiation, or Incendiary—they're ineffective.

Bio-Bulkhead loot drops

Bio-Bulkhead has a dedicated loot pool for three unique Legendaries, plus chances for world-pool items, XP (e.g., 486 at level 15, 2,080 at level 35 UVHM Rank 1), and cash. Drops are RNG-based but farmable via the Encore Machine—expect 5-20 runs for specifics.

Here are the key legendary items Bio-Bulkhead can drop:

  1. Waterfall (Grenade): A Vladof impact grenade causing additional explosions on targets.
  1. Sho Kunai (Grenade): A Jakobs throwing knife grenade that grants stacking movement speed bonuses with hits.
  1. Budget Deity (Pistol): A Tediore pistol producing Combo Orbs on throw, marking enemies for increased damage.
Item Type Notes
Budget Deity Legendary pistol Unique drop from Bio-Bulkhead’s pool.
Sho Kunai Legendary grenade Part of his guaranteed rare-boss loot table.
Waterfall Legendary grenade Also in his loot pool. (

These items are early-game powerhouses, especially for corrosive builds against armored foes.

Bio-Bulkhead farming tips: How to increase your chance for good drops

  • Always farm him via the Big Encore Machine after story mission, so multiple runs increase odds.
  • Bring damage types strong against his armor: corrosive and cryo are best.
  • Maximize your damage during the vulnerable window (after you break the shield).
  • Optimize loot-affecting gear (if the game has items or mods improving legendary drop chance).

Bio-Bulkhead stands out as a boss you can fight early but come back to later, giving access to legendary weapons that help build your arsenal. Knowing where he is, how the fight flows, and what he drops helps turn that repeat battle into reliable loot gains.