Borderlands 4: Blackgrin Boss Location in Pyroclast Grotto

Blackgrin is one of the Occupied Sector bosses on Providence Island, tucked at the bottom of a lava-filled cave system rather than sitting out in the open world. The fight is easy to miss because nothing on the surface points to it — the arena only opens up once you drop through the back end of the grotto.

Quick answer: Blackgrin spawns inside Pyroclast Grotto, an Occupied Sector in the Pyroclast Field region of Providence Island. Shoot the Tediore energy barrier to get in, cross the lava on the jump pad, clear the industrial level, then drop into the cavern at the end of the final tunnel to trigger the fight.

Blackgrin location details

Detail	Value
Boss	Blackgrin
Area	Pyroclast Grotto
Region	Pyroclast Field
Map	Providence Island
Activity type	Occupied Sector (Tediore Lockdown)
Entry gate	Destructible Tediore energy barrier
Enemy faction	Tediore
Fight trigger	Dropping into the cavern at the end of the path

Set your waypoint on the grotto marker inside Pyroclast Field before you head out. The objective tracker will read Explore the sector for most of the run, which is the sign you are still on the correct path.

Route through Pyroclast Grotto to the boss arena

Open the map and zoom into the Pyroclast Field region of Providence Island. Pyroclast Grotto is tagged as an Occupied Sector, so mark it and travel to the cave mouth on foot or by vehicle.

The entrance is sealed by a blue Tediore energy barrier. Shoot it until it breaks — the door objective clears the moment the barrier drops, and the tunnel opens behind it.

Sealed Pyroclast Grotto entrance with the open the door objective showing on the HUD — The sealed grotto entrance with the door objective active. Image: Gearbox Software

Follow the dark tunnels inward. They wind for a short stretch before opening into the lava-filled chambers that make up the middle of the grotto.

Inside Pyroclast Grotto with the explore the sector objective tracked on screen — Inside the grotto, with the explore the sector objective tracking your progress. Image: Gearbox Software

At the first lava gap, look for a green button on the wall. Shoot it to power up the blue jump pad, then step on the pad to launch across.

Work along the metal walkways, pipes, and platforms suspended over the lava. Stay on the structures — falling costs health and sends you back to the last safe ledge.

Narrow grotto corridor with the Pyroclast Grotto location name shown on the HUD — A corridor deeper in Pyroclast Grotto on the way to the industrial level. Image: Gearbox Software

Climb the stairs at the end of the walkways into the open industrial sector. This is where Tediore forces are stationed, and you need to push through them to reach the upper levels.

Firefight against Tediore enemies in the industrial part of the occupied sector — Tediore forces defending the industrial level above the lava. Image: Gearbox Software

On a platform just before the last tunnel sits a Tediore chest. Open it before moving on — it can hand out legendaries such as Hornet Addiction and Soaked Guts, and it is the only loot stop on this route.

Reload prompt highlighted on screen inside Pyroclast Grotto before the final tunnel — Top up your magazine before the last tunnel — there is no cover once you drop in. Image: Gearbox Software

Take the final cave tunnel and drop down into the cavern below. Blackgrin spawns as soon as you land, and the arena becomes the marked point on your map.

How to confirm the fight has started

The drop is the trigger, so there is no switch to flip and no dialogue to wait through. You will know it worked when Blackgrin appears in the cavern with a boss health bar on screen and the arena registers as its own point of interest on the map.

Tip: reload and top up ammo on the chest platform. Once you drop in, the only way out is back up through the cavern, so going in with an empty magazine costs you the opening seconds of the fight.

Why the route stalls

The entrance stays shut because the Tediore energy barrier has not been shot out. It is a destructible object, not a scripted door.
The jump pad does nothing until the green wall button is shot. Standing on an unpowered pad will not carry you over the lava.
The walkway route can look like a dead end if you stop at the industrial level. The path continues upward past the Tediore defenders to the chest platform and the final tunnel.

Run through it once and the layout is short enough to repeat quickly, which matters if you plan to come back for the chest and another pass at Blackgrin.