Board Thread:Lore Discussion/@comment-6702118-20140122184632/@comment-14027812-20140122185459

As said by the article, Mankar can date back to the time of Hjalti Early-Beard. We don't know why he lived so long, but it can be assumed that he spent a part of his life in Oblivion, or that his long lifespan has to do with the fact that he is Dragonborn.