Surtur

King of the Fire Jotunn, and ruler of Muspelheim
While the frost giants of Jotunheim were scattered into several clans this was not the case for the fire giants. Shortly after Ymir's passing his second-in-command declared himself as ruler of the primordial realm of fire. After crushing all who would oppose him Surtur has ruled Muspelheim for eons. 
One day the goddess of death went to Muspelheim and offered Surtur an alliance in exchange for the death of the gods and their followers. Seeing them as his only competition for total control of the nine realms Surtur gladly accepted her offer. During the first battle; however, he was surprised to find out that Loki was none other than the grandson of the only person Surtur bowed before, Ymir. Upon finding this out Surtur vowed to himself that he would not stop until the blood of Ymir rules the nine realms as their birthright.