Gjallarhorn was not merely an instrument used to announce wars or summon Asgard's armies. That was its most famous function, the one that appeared in stories repeated by mortals and in the official records of the Norse pantheon, but the horn possessed far more specific uses. It had been created to transmit a signature through Yggdrasil's routes, ignoring distance, spiritual obstacles, and part of the barriers between the Nine Realms. When sounded by Heimdall, it could alert all of Asgard, call the gods, awaken the Einherjar, and mark a passage for the Bifröst. In the hands of a Valkyrie commander, however, the artifact functioned differently.
Brynhildr could use Gjallarhorn to locate her sisters.
