Borderlands 4 Dark Subject Walkthrough [Step-by-step Guide]

What to know

• Dark Subject is the 13th main mission in Borderlands 4, unlocked after finishing “Something Wicked.”
• The mission takes place across Terminus Range, Windspear, and Kairos.
• Your goals include fighting escaped experiments, unlocking a quarantined lab, and defeating the Vile Prototype boss.
• Rewards include XP, Cash, Eridium, a Rare Pistol, and the Tiger of Partali Vault Hunter style.

BL4 Mission Overview

Dark Subject mission overview

“Dark Subject” begins shortly after you speak with Defiant Calder in Belton’s Bore. You’ll be sent to regroup with Amara and Lilith as they push deeper into the mysterious research facility. Expect dense combat zones, multiple phases of enemies, and one of the trickier boss fights in this act.

Phase A: Meet Amara and defeat the miniboss

Step 1: Return to Defiant Calder

Fast travel to Belton’s Bore and meet Calder. After a short dialogue, the mission officially begins. He warns you that the next zone is crawling with “creeps,” failed test subjects gone rogue.

Step 2: Meet Amara

Head northeast through the rocky pass. Use your grappling hook to climb the cliffs until you reach Amara’s position. She’ll outline the plan — infiltrate the Black Site and locate Lilith.

Step 3: Find Lilith and clear the creeps

Follow the waypoint deeper into the outskirts of the Black Site. This area is packed with small, fast-moving enemies called creeps. They’ll rush you in swarms, so keep moving and use splash-damage weapons to thin them out.

Step 4: Defeat Tim, the mini-boss

Once you clear the first few waves, a mini-boss named Tim appears. He uses energy grenades and teleportation. Focus fire when he reappears from teleport jumps. Defeating Tim unlocks the next zone.

Phase B: Open Black Site and defeat Vile Prototype

Step 5: Break into the Black Site

Head toward the northern end of the arena. Look up and spot a vent covered by a metal grille. Grapple to it, break the cover, and crawl through to enter the Black Site interior.

Step 6: Secure the entrance

Inside, you’ll be ambushed by more creeps and mutated test subjects. Eliminate all enemies to secure the area. You’ll notice multiple terminals but only one active door.

Step 7: Clear escaped experiments

Advance through the corridors. You’ll find containment chambers with glowing glass — these burst open as you pass, releasing stronger test subjects. Expect shock and corrosive variants here. Take them down before they overrun you.

Step 8: Unlock the quarantine lab

After clearing all experiments, locate a terminal beside a sealed lab door. Interact with it to trigger a short sequence and open the door to the Quarantine Lab.

Step 9: Activate the holo-table

Inside the lab, approach the holo-table. Activating it triggers a cutscene featuring holographic research logs revealing the nature of the “Dark Subject.” The logs describe the Vile Lictor’s failed experiment — one that’s still alive.

Phase C: Defeating Vile Prototype boss and escape

Step 10: Defeat the Vile Prototype

This fight is the highlight of the mission. The Vile Prototype starts invulnerable, surrounded by glowing crystals.

Step 11: Clear remaining creeps

After the boss falls, waves of creeps rush in as a final test. Take them out, then approach the console marked on your HUD. Interact with it to trigger the next cutscene.

Step 12: Follow Amara and exit

Amara appears and comments on the destroyed experiment. Follow her outside as she contacts Lilith to regroup. This concludes the Dark Subject mission and unlocks the next story quest, His Vile Sanctum.

Dark Subject mission tips

• Aim for the glowing blue crystals attached to its body. They’re weak points.
• Once destroyed, the crystals float around. Destroy them before they can reattach.
• The boss uses energy bursts and shock waves that punish stationary players.
• Corrosive or shock types deal the most consistent damage.
• Once all crystals are shattered, the Vile Prototype becomes vulnerable. Unload everything you have to finish it off.
• The creeps come in swarms, and area damage clears them quickly.
• The Black Site has tight hallways; strafe and use slides to avoid shock bursts.
• Rocket launchers or high-burst rifles make crystal phases shorter.
• Occasionally, a terminal won’t activate. Fast travel or reload to fix it.

Dark Subject mission rewards

Completing the mission

Once you’ve completed the Dark Subject mission, you’ll unlock access to the next major story arc. It’s one of the darker and more atmospheric chapters in Borderlands 4, blending intense firefights with a taste of horror. With Amara and Lilith back in the spotlight, your journey through the Vile Lictor’s twisted experiments is far from over.