Heimdall

Heimdall is one of the sons of Odin. He keeps watch where Bifröst meets the sky. Ever-vigilant against invaders or Ragnarök, if watched to see if something is coming, and if so, he is to blow on his horn, Gjallarhorn, to warn the gods.

Heimdall and Loki never liked each other. They didn't like each other, even before it was foretold that they would kill one another during Ragnarök.