Surtyr

Background
Surtyr, or Surt, was a frost giant from the realm of Jötunheim, one of the many realms of the plane of Yggdrasil.

Ragnarok
Surtyr was involved in the battle of Ragnarok, which tore the realms apart, killing many of the Aesir, and Vanir gods alike. He led the forces of Jötunheim against the Asgardians. The giant killed the god Freyr, and burned the realms to the ground.