How to get Mehrunes Razor - Elder Scrolls: Morrowind
Location: Yasammidan
Requirements: N/A
Video: How to get Mehrunes Razor
Mehrunes Razor is a short blade given to you as a reward for completing the Mehrunes Dagon's Quest. This quest begins by interacting with the Statue of Mehrunes Dagon in Yasammidan. You can find the Yasammidan Daedric Shrine northwest of Gnisis along the coastline, a map location of exactly where to go is shown below.
With all of the hills and water in this area getting to Yasammidan may be a bit of a chore. I recommend a spell that buffs you Jump skill by 20 - 40 that lasts for about 5 seconds. There are a few spells in game that will buff your Jump like this. It will help significantly with reaching Yasammidan since you will be able to jump from hill to hill while ignoring the water.
Note: There are two Dunmer NPCs inside of Yasammidan that carry Sanguine gear. Loot these items and keep track of them if you ever plan to do the Threads of the Webspinner Quest. Additionally, Anel Rethelas is also part of the Morag Tong Ring of Sanguine Sublime Wisdom quest.
Alas Ancestral Tomb Map Location
After talking with the Statue of Mehrunes Dagon in Yasammidan you'll need to travel to Molag Mar via Silt Strider or boat. From Molag Mar you'll need to travel north to the Alas Ancestral Tomb, an exact location is shown on my map screenshot above. You'll pass the Assarnibibi Shrine on your way here, use that as a marker to let yourself know you're going in the right direction.
The Alas Ancestral Tomb is very small and linear, you'll find the item we're looking for - A Rusty Dagger - on the corpse of Varner Hleras in the back of the tomb. Loot this and return it to the Statue of Mehrunes Dagon to complete this quest and be rewarded with Mehrunes' Razor.