Thin Skin

Select a point you can see within range. All creatures within a 60ft radius of this point make a constitution save. On a failed save, they feel their skin become thinner and more delicate, giving them vulnerability to slashing, piercing, bludgeoning and radiant damage.

This spell has no effect on creatures that do not have skin (e.g. skeletons, stone golems, metal constructs), but does not necessitate exposed skin to cause its effect.