User blog comment:HambleBee/New Concept/@comment-26103034-20160125173457

An ingame item would probably be best. If you choose an in-game thing, then you already have some good lore and story about it's powers. Even if you didn't go for in-game, an already existing lore item would be good.

Data did a really cool RP ages back with the Ebony Blade of Mephala, where various factions and groups are trying to get this weapon. The good thing about Data's was that the Blade corrupted the owner, so that whoever the owner was became the new enemy. The different groups trying to get it was good as well.

As for what it actually is? Perhaps the Ebony Mail, or the blade again. http://elderscrolls.wikia.com/wiki/Daedric_Artifact and http://elderscrolls.wikia.com/wiki/Category:Daedric_Artifacts might help find various existing ones.