Black ice

"Centuries ago, all was lost in the Last Battle when the Norse gods and goddesses went to war. The elves, the giants, and the gods and goddesses themselves were all destroyed, leaving the Valkyrie known as Mist one of the only survivors. Or so she thought. The trickster god Loki has reappeared in San Francisco, and he has big plans for modern-day Earth. With few allies and fewer resources--but the eyes of the gods and goddesses of an old world upon her--it's up to Mist to stop him before history repeats itself"--