For 10 points, identify this Aesir guardian of the rainbow bridge Bifrost.
A now-lost source relates a story in which this god was pierced by a man's head, leading to a new kenning for the word "sword." This figure visited the islands of Vagasker and Singasteinn to fight another deity in the form of a seal in order to retrieve a necklace. This deity lives in the so-called "Heavenly Mountain," Himinbjorg, and he also owns the sword Hofund and rides the horse Gulltop. This god is said to have slept with Edda, Amma, and Modir while under the name (*) Rig; those women then gave birth the ancestors of the three races of man, Thrall, Karl, and Jarl. This golden-toothed son of nine mothers will kill and be killed by Loki after blowing the Gjallarhorn to signal the beginning of Ragnarok. For 10 points, identify this Aesir guardian of the rainbow bridge Bifrost.
A now-lost source relates a story in which this god was pierced by a man's head, leading to a new kenning for the word "sword.
{Heimdallr} [or {Hallinskidi}; or {Gullintani}; or {Vindhler}]