So, on the Boheathia (Dunno if I spelt that right) quest, here is what I did: I got the quest, sacrificed someone, killed everyone, went to shearpoint or knifepoint, killed everyone, took the ebony mail and it still says I have the quest? It says every objective is complete, but the quest is not complete. It has been like this for over a year and it is preventing me from getting the "Oblivion Walker" achievement. Any way to fix this?

This should be in the cheats/hints/spoilers forums ... and not in the general discussion.

Not 100% sure, but ...

If you're on PC, use the console "set stage": setstage .

If you're not on PC, you will need a previous save and re-run the quest.