Loki

The Norse god of mischief, trickery, and fire, a complex and ambivalent figure who is a Jotunn (giant) by birth but blood-brother to Odin. He constantly creates problems through his clever schemes, but also sometimes helps the other gods.  He is the father of monstrous offspring, including Fenrir, Jörmungandr, and Hel, and ultimately instigates Ragnarok.