How to Beat Bio-Bulkhead in Borderlands 4

Bio-Bulkhead is a heavily modified version of the standard Bulkhead enemies you’ve encountered before. Its key feature is a layer of super armor that makes it completely immune to all damage. To even begin chipping away at its health, you must first remove this protective layer. This fight is a test of your mobility, awareness, and ability to manage the arena’s unique environmental tools.

The boss has two primary health bars: a yellow armor bar and a red health bar underneath. Once you strip its immunity, you will need to burn through both to achieve victory. Corrosive weapons are highly effective against its yellow armor bar.

The Locust Canister Mechanic

The single most important mechanic in the Bio-Bulkhead fight is the use of locust canisters. These are the only ways to remove the boss’s immunity and make it vulnerable to your attacks.

Finding the Canisters

There are two consistent spawn points for locust canisters in the arena. It is vital to learn these locations so you can quickly grab one whenever the boss regenerates its immunity.

• Inner Room Canister: Located next to a pillar in the inner part of the room, identifiable by its reddish lighting.
• Outer Wall Canister: Found along the outer wall of the arena, in an area with more bluish lighting.

You must use your grapple to grab these canisters and then throw them directly at the Bio-Bulkhead. A successful hit will temporarily strip its super armor, opening a window for you to deal damage. You will know the armor is gone when you no longer see the word “Immune” appearing when you shoot the boss.

Bio-Bulkhead’s Attack Patterns and How to Avoid Them

Surviving this encounter means learning to recognize and dodge Bio-Bulkhead’s aggressive attacks. Staying mobile is key, as most of its moves are designed to punish stationary players.

Long-Range Jumping Attack

Bio-Bulkhead will crouch low before leaping across the entire arena to slam down on your position. This attack is powerful but predictable.

• How to Avoid: The boss cannot change its trajectory mid-air. As soon as you see it jump, sprint, or dash in any direction to easily evade the impact. Be mindful that the slam leaves behind an elemental hazard on the ground, so watch your step after dodging.

Elemental Energy Waves

From a distance, the boss will slam its hands together and fire a series of horizontal energy waves that travel along the ground.

• How to Avoid: You can simply jump over these waves. Alternatively, backing away can work as they have a limited range. The pillars in the room also provide excellent cover from this attack.

Ground Slam Waves

Similar to regular Bulkheads, this boss can slam the ground to send out yellow energy waves that ripple across the floor.

• How to Avoid: A simple jump will clear these waves. However, always be aware of where you will land to ensure you don’t drop into another hazard or right in front of the boss.

Elemental Slam AoE

Bio-Bulkhead will jump straight up and slam back down in place, creating a large area-of-effect (AoE) elemental puddle and a damaging shockwave.

• How to Avoid: This move is telegraphed by the boss jumping vertically. As soon as you see it leave the ground, backpedal or dash away quickly to get out of the blast radius.

Strategy for Defeating Bio-Bulkhead

Now that you understand the mechanics and attacks, let’s put together a winning strategy. This fight revolves around a consistent cycle: stripping the armor, dealing damage, and avoiding attacks until the armor returns.

Phase 1: Removing the Locust Armor

Start the fight by immediately heading to one of the locust canister locations. Grapple a canister and throw it at the Bio-Bulkhead. This fight is impossible until you remove its initial immunity, so make this your top priority.

Phase 2: Damage and Evasion

Once the immunity is gone, switch to your strongest weapons, preferably with Corrosive damage to melt its yellow armor bar. The boss’s head is its critical hit spot, so aim there to maximize your damage output.

While attacking, never stop moving. Constant backpedaling and strafing are essential. The Bio-Bulkhead is relentlessly aggressive and will always be running or jumping toward you. Use your glide pack’s dash ability (Circle/B on controllers, Left-Shift on keyboard) frequently, both on the ground and in the air, to maintain distance and create space.

Listen for audio cues and watch the boss’s animations to anticipate its next attack. Your focus should be on survival first and damage second.

Phase 3: Rinse and Repeat

After a short period, the Bio-Bulkhead will regenerate its locust armor, and you will see the “Immune” text pop up again. This is your signal to stop shooting and repeat Phase 1. Disengage from the boss, grab another locust canister, and strip its armor once more.

You will need to repeat this cycle several times. The fight becomes more intense as weaker grunt enemies begin to spawn in the arena. While they add another layer of pressure, they are also a valuable resource. If you enter “Fight For Your Life,” you can quickly kill one of these grunts to get a Second Wind and return to the fight.

By staying mobile, prioritizing the locust canister mechanic, and consistently hitting critical spots, you will wear down the Bio-Bulkhead and emerge victorious. Once it’s defeated, be sure to collect your well-earned loot, which can include Legendary items like the “Waterfall” grenade mod.