It's a made up item for the Hoard collection, along with the dragon priest masks Bahlok (obtained by playing The Labyrinth), Onikaan, and Sahvot. They have played into various events that have taken place across the site over the years.

The "lore" behind the blade is that it belonged to an Akaviri warrior who defeated the aforementioned dragon priests. It can be obtained by locating a hidden room in Forelnaar.

oh ok cool