What is the Ancient Vampire Sword for in Skyrim?

A friend of mine found this sword in their inventory, and it is marked as a quest item. It is in the Miscellaneous section, however, rather than weapons. We believe it is from a mod, but are unsure which mod it is from, and also cannot figure out what quest it belongs to. Can anyone help?

screenshot of item in the inventory in-game


Solution 1:

It's from the Better Vampire NPCs mod, specifically the Coldhaven quest, and according to the mod author is in the game as a quest item (hence in the Miscellaneous section) because:

"One of the houses wants you to retrieve it."