Brother in Need
Head over to Karoosh's map marker to the north east of your village.
Upon arriving at the marker, you will find an injured wenja warrior. He tells us the Udam are fighting against a lone warrior and asks if you can help him.
Head over to the marked area to find Karoosh taking on some Udam.
Help him kill them and you will get to meet Karoosh and he then talks about himself and an Udam warrior who killed his son. He asks that you help him do this.
Now you must pick up Udam bodies and throw them into the fire in the middle of the area. Do this by Holding R3 over an opponent's dead body and press the same button to toss them into the fire.
After tossing in three bodies, simply kill all the remaining Udam.
Survive and eliminate all the Udam attackers to have Karoosh join your village and complete the mission.