This quest comes up as part of the main storyline. Go to the refugee camp at the entrance to Sunfall and speak to Vanasha to find out about Uthid. Once you’ve finished talking to her, follow your waypoint marker to the three dead trees. When you get there, scan with your Focus to find his tracks and follow them up the mountainside.
When you reach his camp, investigate it, then continue following his tracks back down the other side of the mountain. Investigate the destroyed Grazer, then take out the three Glinthawks that turn up the scavenge the corpse. Once they’re down, keep following his trail until a cutscene triggers. When it’s over, go talk to Uthid. At the end of the conversation, the first band of mercenaries will show up. They’re roughly split into melee and ranged attackers, but it can be easy to miss the melee enemies until they’re right on top of you, so stay alert.
Kill the mercs until they stop coming, then follow Uthid up and over the ledge. Gather what supplies you can and get ready for more mercs attacking. Again there will be a melee/ranged split, but this time the melee lot will be coming from two directions. One down the mountain in front of you, and off a zipline to the left, so keep watch on both of those as you fight.
When they’re all dead, once again follow Uthid up and over the ledge. This time you’re facing 3 Elites, one with a Firestriker weapon and another who’ll shoot Corruption arrows at you. The blast sling is a great weapon to use here as even if a blast doesn’t kill them, it can knock them off their feet and take them out the fight for a few moments whilst you deal with one of their comrades.
When they’re down, climb up the ledge and talk to Bahavas and that’s this quest done and dusted!