Sword of Despair

Upon casting this spell and touching a melee weapon, it is imbued with purple necrotic energy. Your weapon is enchanted with necrotic damage for the next 1 minute of concentration or until dropped. Your weapon now deals 2d10 necrotic damage per hit and on a critical hit, the creature you hit is frightened of the user for 1 round.

For every spell level above 2nd, add 1d10 onto the damage die.