Obtain it, and then find the word wall behind a large altar. Mehrunes Dagon is the daedric prince of Destruction. After the Dragonborn has acquired the pieces of Mehrunes' Razor, Silus Vesuiusexplains that in order to repair the Razor, the daedric lord himself must be contacted. This has no signpost and can be overlooked if you're not watching for it. Take the road uphill then bear right at the fork you will soon encounter. A pressure plate activating another fire trap awaits the unwary on the floor of this hall. Evidently, it depends on your position when speaking to Mehrunes Dagon.

This forces the player to complete the 'Pieces of the Past' quests to get to the spells. Your goal is to reach the entry door to the interior of Hag Rock Redoubt before encountering any enemies.