This walkthrough covers the full main story quest “The Chase” in Borderlands 4, including every objective, enemy encounter, and the exact path to the boss fight. You’ll get the complete step-by-step route, loot tips, and how to unlock the next mission.
Quest Overview and How to Start
“The Chase” is a main story mission that becomes available after you complete the previous story quest, “The Vault Key Fragment.” You must be at least level 12 (though 14 is recommended) and have unlocked the planet Promethea. The quest is given by Lilith in the Sanctuary III bridge. She will tell you that a rogue AI has stolen a vital piece of the Vault Key, and you need to chase it down through the Meridian Outskirts before it reaches the city core.
Objective 1: Locate the Rogue AI’s Signal
After the opening cutscene, your first objective is to follow the signal to the Meridian Outskirts. Fast travel to the Meridian Outskirts entrance. From the spawn point, head north toward the industrial district. You’ll see a large satellite dish on a hill—that’s your first waypoint. Along the way, you’ll encounter a handful of COV bandits and a few Skag packs. Use cover and pick them off from range; they don’t have any heavies yet. Once you reach the satellite dish, interact with it to triangulate the signal.
Objective 2: Enter the Abandoned Robotics Facility
The signal leads to an old Hyperion robotics facility. The entrance is a large blast door on the east side of the district. You’ll need to defeat a mini-boss, “Foreman Jasper,” who guards the door. He’s a mid-tier badass with a rocket launcher. Keep moving, use the pillars for cover, and aim for his exposed fuel tank on his back. After he drops, loot his body for a guaranteed epic grenade mod. Then, open the door and enter the facility.
Objective 3: Navigate the Facility and Solve the Security Puzzle
Inside, the facility is a linear corridor with several rooms. In the third room, you’ll find a security console that requires a 4-digit code. The code is randomly generated each playthrough, but you can find it on a whiteboard in the same room (look for the glowing marker). Enter the code to unlock the next door. After that, you’ll face a wave of loader bots, including a few “Surveyor” drones that hover. Shoot their red eye to disable them quickly. Continue through the maintenance tunnels until you reach the central server room.
Objective 4: Boss Fight – The Rogue AI (BL4-7N)
The final room houses the rogue AI, designated BL4-7N. This is a two-phase boss fight.
- Phase 1: The AI is housed in a large central core. It will spawn adds (loader bots and a few badass variants) while firing slow-moving energy orbs. Destroy the four shield generators located on the corners of the room to bring down its shield.
- Phase 2: Once the shield is down, the core opens, revealing a glowing weak point. Shoot it until it closes, then repeat the process. The AI will also start using a ground slam attack—jump or get behind cover when you see the floor glow red.
After you deplete its health bar three times, the AI core will explode, and you’ll get a cutscene. Loot the room for a guaranteed legendary class mod for your current character.
Rewards and Next Steps
Completing “The Chase” rewards you with a significant amount of experience (roughly 1/3 of a level at level 14), a rare-quality shield, and a few thousand dollars. You also unlock the next main story mission, “The Great Vault,” which is given by Lilith back on Sanctuary III. Before you leave, make sure to explore the facility’s side rooms—there are two red chests hidden in the upper walkways that require a bit of platforming to reach.
Frequently Asked Questions
Can I skip the security puzzle?
No, the puzzle is mandatory to progress. However, the code is always in the same room, so you don’t have to backtrack. Look for the whiteboard with a glowing marker—it’s usually on a wall near the console.
What level should I be for this quest?
The enemies scale to your level, but the recommended level is 14. If you’re under level 12, the boss fight will be tough. Grind a few side quests in the Meridian Outskirts to level up.
Is there a way to get the legendary drop more than once?
The legendary class mod is a guaranteed drop on your first completion. If you want another one, you can reset your playthrough (TVHM or Mayhem mode) and replay the quest, but it will require you to redo the entire story up to that point.
Where are the hidden red chests?
There are two red chests. The first is on a platform above the security puzzle room—use the crates to jump up. The second is in the final boss room, on a ledge to the left of the entrance. You’ll need to jump across the broken pipes to reach it.
My game crashed during the boss fight, will I lose progress?
No, the game auto-saves at the start of the boss fight. When you reload, you’ll be back at the facility entrance, and the boss will be at full health, but you won’t have to redo the earlier objectives.
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