To get this achievement you have to make it to The Thorniara part of this game & then breeze threw the majority of that area doing quests & the like, make it to the part where diego & hagen are taken to the arena, find those two talk & tell them that you will fight for them in the arena instead of them. Do that Kill Drurhang then talk to the ghost & the cheevo should pop. The cheevo is story related so you should not miss it. Thats it have fun.