Hasskor was the leader of the Ice Warriors on Coldstar. He was a member of the Ice Lord class and the Sectarian Cast. He was planning to tale revenge on the humans for the destruction of his people by crashing Coldstar into the planet.
Hasskor coerced the Tenth Doctor into allowing him into the TARDIS. He explained to the Doctor that the humans burned his world and that's why he wanted revenge. Lorna explained to him that some of his people survived. Knowing that he no longer need to seek revenge, he died but he set his self-destruct mechanism in his suit in order to kill the Doctor. (AUDIO: Cold Vengeance)