This quest immediately follows Into the Borderlands. Head for the Sun Palace and talk to Avad and Erend. When the conversation is over, follow your waypoint to the warehouse where a cutscene will trigger. Back in control, investigate the bomb then head upstairs. Scan and investigate the larger blaze stash, then just to left of that there’s a latch. Investigate that to open the doors then examine the barrels to start another cutscene.
When you’re back in control, scan with your Focus to find the tracks. Highlight them and follow. They’ll lead inside a building and downstairs where there will be a section of wall missing. Pass through the hole in the wall and go down the cliffside to trigger another cutscene. When you’re back in control, hope up onto the climbable ledge then head left along the side of the cliff towards the bridge. Cross the bridge and take out the two guards that were left behind.
With them down, follow your waypoint up to the Solarium where a cutscene will trigger. Back in control, destroy the noise making device then head after Dervahl and his men. There will be a short cutscene, then you’ll have to fight them. Dervahl has a Tearblaster, which does damage and knocks you down, and his two cronies will alternate melee and blast sling bombs. Use the circular terrain to your advantage to break them up if you’re getting overwhelmed, and set traps and blast wires behind you so if they pursue they’ll get punished for it.
When they’re all down, another cutscene will have Dervahl call in a bunch of Glinthawks on top of you, so you’ll have to kill them too. As usual with Glinthawks, either hit them with Tearblast arrows in the Freeze sac to freeze them and bring them down for a critical, or use a Ropecaster to tie them down and hit them that way. One useful thing to do is to Ropecast one down and override it so it keeps at least one other Glinthawk distracted as you fight.
When all the Glinthawks are down, talk to Dervahl again to start another cutscene, then talk to Avad, Erend, and Dervahl again (Dervahl is optional but worth it) to complete the quest, and this particular quest line.