The Elvenking, @, is a monster in NetHack - the strongest of the elves. As with all elves, their corpses have a chance to grant intrinsic sleep resistance and they can be generated with any type of elven equipment of which they will make use. In addition, they can be generated with a pick-axe (especially on special levels) and, very rarely, a crystal ball. As almost all monsters, they can have offensive and defensive items, e. g. a wand of death.
Elvenkings appear on the list of nasties; this can result in some confusion as they share the glyph of the Wizard of Yendor. There is a guaranteed Elvenking and appearance of the Wizard on the Plane of Earth, adding to the problem.