Vápnthjófr saga

After Balder was made invincible, the gods celebrated by throwing weapons at him (as you do) to watch everything bounce off. Loki donned a disguise and asked Frigga if there really was nothing that could harm him. She answered that she hadn’t asked the mistletoe, since she thought it was too small and harmless to bother with. Upon hearing this, Loki fashioned an arrow from mistletoe and went up to Höder, Balder’s blind brother, who was standing off to the side. He asked him why he wasn’t participating in the other god’s fun, and he answered that he couldn’t see where Balder was standing. Loki offered to help him aim, and gave him the mistletoe arrow. Upon being hit by it, Balder fell dead to the ground, and he got a burial where everyone mourned him. (The doe lying beside him is his wife, who died of heartbreak upon seeing his body on the pyre- This time, it’s not a sacrificed thrall!)