Definition
Heimdal is simply an alternative spelling of Heimdall, the Norse god who guards the Bifrost bridge connecting Asgard and Midgard. He is known for his exceptional senses and unwavering vigilance. Essentially, "Heimdal" and "Heimdall" refer to the same figure in Norse mythology. Using either spelling is generally acceptable, though "Heimdall" is more common. Think of it like spelling "gray" or "grey".