In Norse mythology, Freyr lacks his sword when he faces Surtr at Ragnarok. He had previously given the weapon to his servant Skírnir as part of a bargain connected with his courtship of Gerðr.
The sword is important because it is described as capable of fighting by itself. Without it, Freyr must fight Surtr with a stag’s antler in the final battle and is killed.
This episode connects an earlier love story to the apocalypse: Freyr’s decision to surrender the weapon eventually leaves him vulnerable. Some modern retellings simplify the story by saying only that he loses his sword, without explaining why.
Freyr is a fertility and prosperity god, not primarily a war god, which makes his doomed confrontation with the fire giant especially striking.