Borderlands 4 scatters nine Vault Key Fragments across Kairos — three apiece in the Fadefields, Terminus Range, and Carcadia Burn. Collecting a region’s three fragments opens its Primordial Vault, a multi-stage dungeon with a boss at the end and, after completion, a jetpack upgrade. You can brute-force the hunt by exploring, or use Order SILOs to narrow the search radius and glide straight toward each fragment with a tethered balloon. Either way, the fragments are fixed spawns once you know where to look.

Vault Key Fragments and Order SILOs: how the tracker actually helps

Order SILOs are optional but efficient. Claiming a Silo marks a large circle on your map for the fragment tied to that Silo’s area and enables a proximity scanner — it behaves like a hotter/colder hint as you move. Most SILOs also give you a balloon lift so you can glide to hard-to-reach perches, and they unlock a fast travel point plus SDU credits when claimed. Importantly, you do not need to activate a Silo to pick up a fragment; the collectibles are present regardless.

One exception where the Silo lift meaningfully simplifies access is in Terminus Range’s Cuspid Climb, which places a fragment beyond an easy jump path. Use the balloon to cross a gap to a rock bridge, then drop into a cave to secure the item.

Fadefields vault key fragment locations (3)

  • Coastal Bonescape (southwest corner): Near the Stillshore point of interest, look for a building with a slowly rotating fan. Check the back balcony; the fragment sits on a marked crate.
  • The Howl (north of The Launch Pad): Find the small cave between Ardor’s Bounty (to the northeast) and The Launch Pad (to the southwest). Enter from the north; the fragment rests on a pedestal among the rocks.
  • Idolator’s Noose — Rosemary’s Reserve: Head to the Propaganda Tower in Rosemary’s Reserve, then go slightly southeast to a loose vent panel. Pull the vent to open a crawlspace leading to a stash room. The fragment is in the south corner under red lighting; expect a bobblehead nearby as well.

Terminus Range vault key fragment locations (notable spots)

  • Cuspid Climb (central ridge): Claim the Reliquary Silo to access its balloon. Before lifting off, face north toward a rock bridge jutting from the mountainside near a waterfall. Glide over, then push northeast into the cave. Be ready for a unique Mangler or a dynamic Rift encounter.
  • Windspear — Order base interior: Starting from the Heritage Opus safehouse, approach the facility and enter on the left side. Navigate to the computer room; the fragment lies on a table among the terminals. The Vestal Garrison in this area is heavily patrolled, so clear resistance as you move inside.
Tip: If you’re missing the third fragment here, use the nearest Silo’s scan radius and balloon glide to sweep high ledges and cave mouths along cliff faces — the tracker’s proximity pings make it faster than combing the valley floor.

Carcadia Burn vault key fragment locations (notable spots)

  • Lopside — One Pumper station: North of The Yawning Yard, find the gas station with the “One Pumper” sign. Use the Grapple Node above the canopy to reach the upper level. The fragment is on a long table on the second-tier platform.
  • Tonnage Peel — Wreck of the Last Great Hope: Search the wreck site’s interior compartments and exposed decks; the fragment spawns within the point of interest rather than out in the dunes. Work methodically room by room to avoid misses.
Note: Carcadia Burn’s remaining fragment follows the same pattern as the other zones — activate the nearby Silo to draw a search circle, ride the balloon, and let the scanner steer you as you sweep elevated catwalks and broken overhangs.

What finding all fragments unlocks

With three fragments in hand for a given region, the Primordial Vault in that zone becomes accessible. Vaults function as compact dungeons with layered combat arenas culminating in a boss. Clear rewards include high-end loot and a jetpack upgrade after completion. While you can farm vault bosses once unlocked, you’ll need to repeat the fragment process across all three regions to open every vault on Kairos.

Quick troubleshooting for tricky fragments

  • Can’t reach a ledge: Check for a Silo balloon or a Grapple Node nearby; many fragments are placed to favor vertical approach rather than platforming up from below.
  • Scanner isn’t narrowing: Stay within the Silo’s circular search area; the hotter/colder feedback only activates inside its boundary.
  • Area feels empty: Revisit the exact nooks: behind vent panels, inside cave pockets, and within indoor computer rooms. Several fragments are placed just out of line of sight behind a single pull or turn.

If you prioritize the Fadefields first, you’ll unlock your initial vault early, then use its rewards to speed up hunts in Terminus Range and Carcadia Burn. From there, SILOs keep the remaining fragment chases focused: claim, balloon, scan, grab, repeat.