Death Blade

You enchant a blade you wield with a slain soul. If you have slain an enemy in the last turn, you can cast this spell as a bonus action, otherwise it has a casting time of 10 minutes. Until the start of your next turn, a bladed weapon you wield gains a +2 bonus on attack rolls and damage rolls. A creature hit by this weapon must succeed on a Wisdom saving throw or become frightened of you until the start of your next turn.