- Go to the "Area South of Lighthouse" (Archaeological Site)
- North East of the Center is a digsite. Talk with Charleston Nib and accept his offer to guard the site.
- Speak with Gallor, if he doesn't automatically speak to you first. ACCEPT his request to kill Charleston but DO NOT kill Charleston yet.
- Speak with Charleston again, a short cutscene should play
- Kill all the "Diggers"
- Attack and kill Charleston.
- Open the sarcophagus and take the Idol of Kozah
- Go outside and immediately speak with Gallor before the Doomsayer attacks
- The achievement will unlock after the dialog box has ended. You do not need to kill the Dommsayer for the achievement (although it does give a lot of XP if you manage to end it)
Note: The companion to this achievement will be unobtainable without a save reload.
This achievement can be done immediately afterwords if you have the idol.