In Norse myth, Gjallarhorn is the "ringing horn" with which the gatekeeper god, Heimdallr, announces Ragnarök.
At the peak of the mountain, the wreckage of what appears to be a rocket-powered vehicle is half-buried in the snow, surrounded by several gnome-sized skeletons along with empty bottles and fish skeletons, presumably the crew's last meal before dying of exposure and starvation.