Board Thread:Lore Discussion/@comment-25273173-20140512152513/@comment-31396746-20170331095427

Haldriin was the dragon priest of Bleakrock isle entombed in SkyShroud barrow. The isle only appears in online as the idea was made for online. It can't even be seen on a map in later games. You couldn't fight him anyway because the Vestige destroyed his body, along with his mask.