Assess Creature (Ptolus)

You wave your hand at a creature within range; if the creature fails a Wisdom saving throw, you learn how many Hit Dice it has and (if an NPC or monster) its challenge rating. The spell automatically fails if the creature is using any type of magical disguise, polymorph, or shapechange (although you don’t know if it failed because the creature made its saving throw or because it is magically disguised).