Here are a few ways to use "enigma" in an adjectival way:
* Use a phrase:
* "enigmatic" - This is the most common way to describe something as mysterious.
* "of enigmatic nature" - This is a more formal way to describe something as mysterious.
* Use "enigmatic" as a noun:
* "The painting was an enigma, full of hidden meanings."
Let me know if you have another word you'd like to turn into an adjective!