Valhalla = a hall in Ásgarð where Óðin offers hospitality to those who died in battle.

Valkyries = Sometimes called shield-maidens or maidens of Óðin, these women live in Valhalla and offer mead to the dead who come there. It is also up to them to determine the course of war and summon the fallen men to Valhalla. Those men are called the Einherjar.

Einherjar (or Einherjer) = Óðin’s champions. They battle every day in the courtyard of Valhalla in preparation for Ragnarök.
"Who stole the Einher from the Einherjar?" Sorry.