When you go to kill the 10 trolls just before the troll king, you simply have to deal a few points of damage to them, then run away and let the warriors accompanying you finish them off. For some reason it marks them as if you had killed them yourself. Also, the troll king didn't attack with melee at all when I fought him, but he did have a nasty range attack and a very poor magic attack that held you in place for like a second. Your best bet: Use the prayer potions they give you and you'll be fine with just them, use a poisoned weapon (ddp+ is what i used), and you only really need like 4 lobsters (although you'll need more for the trolls in the beginning). I finished this quest at 73rd level with ease.
