Horsa

It is more than likely possible that he was the brother of Hengest and that, together, they were mercenaries in the army of King Vortigen (Arthur??) of legend. The old Germanic legends based on Horsa and Hengest may be based on their combat adventures with King Vortigen against the ancient British Picts in the 5th and 6th centuries.

See the article on Horsa and Hengest in Wikipedia for furthur info.