The Valkyrie are warlike virgins, mounted upon horses and armed with helmets and spears. Odin, who is desirous to collect a great many heroes in Valhalla to be able to meet the giants in a day when the final contest must come, sends down to every battle-field to make choice of those who shall be slain. The Valkyrie are his messengers, and their name means "Choosers of the slain." When they ride forth on their errand, their armor sheds a strange flickering light, which flashes up over the northern skies, making what men call the "Aurora Borealis," or "Northern Lights." [Footnote: Gray's ode, "The Fatal Sisters," is founded on this superstition.]