Chthonic
Adjective.
Also Chthonian.
Of or relating to the underworld.
Of or relating to the deities, spirits, and other beings dwelling under the earth.
[Origin: from Greek khthonios in or under the earth, from khthōn earth.]
1840-1850.
“What’s bi-sub syndrome, anyway?” “Don’t know. I tried to look up some of Dr. Abraham’s work and found something titled ‘The Evolution of Hierarchical Behavior Expressed Through Chthonic Fetishization,’ and gave up after that. I don’t speak academic fluently enough.” – The Killer Wore Leather, Laura Antoniou.
I love this one. I totally want to use it even though it is probably beyond me do so without being ridiculously pretentious.
Oh, you’ll find a way to use it! It’s a grand word. :D It even has its own wiki: https://en.wikipedia.org/wiki/Chthonic