Centipedes and Spiders are from the Fey Realm, but were long ago banished to the Underworld. Most of the Centipedes and Spiders, while larger than in the World We Know, are still merely beasts. There are some of these creatures who are ancient, and these have grown huge over the countless years since they were cast into the Shadow Realm and their intelect has grown with their size.
The many-legged centipedes accepted their place in the Shadow Realm and sometimes even sell whatever information they can gather about the Lords of the Underworld and the Court of the Black Citadel to the highest bidder, which is often the Kings and Queens of the Fey.
The centipedes eight legged cousins, however, have not forgotten their banishment from the shadows of the Green Realm and they hate all fey creatures with an unquenchable seething and malicious passion.