Hranvard Frostfinger

 was a witch of Eastmarch who was said to have sacrificed thriteen innocent people at once to the Daedric Prince, Mehrunes Dagon, which briefly opened a portal from the Deadlands to Skyrim. Hranvard was slain quickly afterwords by the witch hunting Direfrost Family. But after she died the sky split apart and engulfed the witch hunters in flame killing all thirty of the hunters except for the leader, Yllothon, who was spared by what was probably Dagon only so he could agonize over the loss of almost his entire clan.