The Einherjar were Odin's half of the battle slain. Warriors that would fight alongside him at Ragnarok against the enemies of the gods. The Valknut is the symbol on the back of this shirt and it's one that should not be taken lightly. By wearing this symbol you are making the statement that you are ready to die in battle. This is why you see it tattooed on many who are devoted as warriors to the Allfather. TILL VALHALL!!