An Inversegen, also called a Devil Fish, is a 5-foot tall manta ray-humanoid hybrid. Its head is encased in a large fin with a span of 7 feet. It has black beady eyes and a large mouth filled with two rows of needle-like teeth. It has small, almost vestigial arms and fully-formed legs, both without skeleton and a long spiked tail. Its coloration varies from auburn to rosewood.

An inversegen only speaks its native language. It can be found only in salt water and lives in open cities at the bottom of the oceans where it is said to worship evil sea gods.