Deep Magic Volume 2 (p.210)
Power Word Vulnerability
2-level Transmutation
Casting Time: 1 action
Range/Area: 60ft.
Components: Verbal
Duration: Instant
Attack/Save: WIS Save
You utter a word of power and one creature you can see within range becomes vulnerable to one of the following damage types of your choice: bludgeoning, piercing, or slashing. If the target is normally immune to the chosen damage type, it has resistance to that type of damage instead. The target must make a Wisdom saving throw at the end of each of its turns. On a successful save, this vulnerability ends.
Available for: Bard, Sorcerer, Warlock, Wizard