Mana Break

3rd-level Transmutation
Casting Time: 1 bonus action
Range: Self
Components: V
Duration: (C) 1 minute

The next time you hit a creature with a weapon attack before the spell ends, your weapon crackles with hungering arcane energy that burns a spellcaster that has already tapped into their natural energies. The target must make a Wisdom saving throw or take an amount of extra arcane damage equal to the mana they have spent, or half as much damage on a successful saving throw. A creature with innate spellcasting or other similar abilities does not take any extra damage from this spell – only creatures with spellcasting.

Source: Homebrew