Upon Death, the Dark Elf Reverts to its Natural Form…
If you want to know what this creature is, make a DC 15 Intelligence (Nature) check. Success reveals that [the creature is a doppelganger, a creature that can change its appearance to match another creature as tall or smaller than itself].
If the result of your check is 20 or higher, [you also know that this creature is capable of reading the surface thoughts of other creatures].
If the result of your check is 25 or higher, [you have access to all information from the doppelganger’s stat block].