In the world of the Elder Scrolls, without question the most powerful items are Daedric Artifacts. These relics are connected to the most powerful of Daedra, the Daedric Princes, and the items share their power. In this series of post, I will upload the most powerful items in the world of Elder Scrolls, here is the first one, Mehrunes' Razor
Weapon (dagger), Legendary, Requires attunement
You gain a +3 bonus to attack and damage roll you make with this weapon.
This ebony dagger was created by the Prince of Destruction, Mehrunes Dagon, and it bears a powerful enchantement, as it has a small chance to kill any target struck with it instantly. Every time you hit a creature with the Razor, roll a d20. On a roll of 20, the target is automatically slain. This does not affect constructs.
This Daedric Artifact appears several times over the course of history, always followed by bloodshed.
As all Daedric Artifacts, the razor also shows tendency to disappear from history from time to time, and reappear at unexpected places. Presumeably the Lord of Destruction can also call the artifact to himself anytime he wants it.
The razor might lay around in a dungeon, covered with cobwebs, or the players might have to do a small (or large) quest for Mehrunes Dagon himself to acquire it.
The art belongs to its respective owner. Here is his deviantart profile: http://drummerguy-souris.deviantart.com/