Source: City in the Deep, pg(s). 88-89
An enisysian appears as a small grey tentlike creature with six tentacles that end in small hooks. Its upper body is jellyfish-like, with three large, lidless eyes with vertical black pupils arrayed in a line. On the underside of its body is a small double-hooked beak for eating and attaching to its host. On land, it uses four tentacles as legs and two others as arms. In the water, the enisysian propels itself with its tentacles like a squid.
A typical enisysian is about three feet in length and weighs approximately 40 pounds.
The first enisysians were bred from aboleth stock in the aftermath of Earthfall by the Fifth Dictum. Having always been opposed to the human experiment that was the Azlanti civilisation, the members of the Fifth Dictum began breeding the enisysians as subservient slaves so they would have the power to intervene against their own kin and prevent such a disastrous decision from ever being made again. They have kept the existence of the enisysians secret from the rest of their people at large, rightfully fearing the outrage should it become known that they have bred alghollthu slaves.
For millennia, the enisysians, who were bred for dedication and obedience, have never communicated with anyone else other than their bonded veiled masters. This has begun to change over several centuries, as natural mutations have decreased the enisysians' subservience and enhanced their self-awareness. Individual enisysians have begun to secretly communicate and awaken others to their enslavement while seeking support from other alghollthu. Although their emancipation has been very slow due to the Fifth Dictum's paranoia and secrecy, knowledge of their existence has begun to spread among the aboleths at large as well as to surface scholars.
Enisysians coexist with their masters in an asymmetrical physical and psychic symbiosis. Each is custom-bred to serve a single veiled master for life. Like other alghollthus, an enisysian is nearly immortal, able to heal almost all wounds over time or enter a chrysalis state to wholly regenerate. Designed and bred to be subservient, an enisysian allows itself to be attached to its veiled master host at a young age. Once the bond is formed, the enisysian disguises itself as a suckerfish and remains attached and disguised until death.
Enisysians draw nutrition by filter feeding the water and by drawing from its veiled master's blood. In exchange for their protection, the much weaker enisysians grant their veiled master hosts not only increased mental capacity but also the ability to use their powers to influence other alghollthus.
The existence of enisysians as slaves violates the second dictum of the alghollthu people: an alghollthu is to control. It should therefore never be controlled. Members of the Fifth Dictum rightly fear that should it become known that they created a race of alghollthu slaves, their kind would quickly turn against them. Until very recently, enisysians have had no cultural or personal identity separate from that of their masters and communicated with no one else, though this has started to change.