Your goal here is to stealth-kill the marked Olog hai, with optional goals to not kill any other orc (easy), and to remain completely undetected (trickier).
You'll notice the first olog's patrol will bring him right up the tower you start on. Aerial stealth attack, then scamper right back up the tower.
Sneak along the rope down-cavern, behind the archer's back, and backstab the olog there.
Sneak through the hut for kill three.
Now stay low and go back through the hut. Keep to the edge of the camp as you move counterclockwise through the cavern to dispatch the remaining two targets.
These kills complete the mission.
