A dagger in the back might hurt for some time, but the pain of a woeful dagger never ends. You conjure a woeful dagger in your free hand, which lasts for the duration.

You are proficient with the woeful dagger and you may use your spellcasting ability instead of Strength for the attack and damage rolls of melee attacks using it.  It deals 2d4 piercing damage and is a magic weapon.

Once during the spell's duration, when you hit a creature with the woeful dagger, you can make a woeful stab. The creature you hit must make a Charisma saving throw. On a failure, you deal an extra 3d10 psychic damage and the target has disadvantage on saving throws for one minute. The affected creature can repeat the saving throw at the end of each of its turns. On a success, the effect ends.

credit to zst0rm