For ten points, name this Norse god who lives in Himinbjörg, at the entrance to Asgard, and guards the rainbow bridge, Bifröst.
He has nine mothers, all sisters. His skin is the whitest of all the gods, his teeth are made of gold, and he rides a golden-maned horse named Gulltopp. He once turned himself into a  seal to retrieve the necklace Brisingamen of Freyja's that was stolen by Loki. He will blow his trumpet, the Gjallarhorn, to signal the start of Ragnarök, when he and Loki will slay each other. For ten points, name this Norse god who lives in Himinbjörg, at the entrance to Asgard, and guards the rainbow bridge, Bifröst.
He has nine mothers, all sisters. His skin is the whitest of all the gods, his teeth are made of gold, and he rides a golden-maned horse named Gulltopp.
Heimdall ( or  Heimdallr)