Symbiont

A symbiont is a type of creature that lives in a conjoined nature with a host creature, either as a parasite to feed off the host creature or to provide abilities that benefit the host creature.

In the EMPATH: The Luckiest Smurf story series, the Nocturnians act in the role of symbionts with a parasitic nature in regards of requiring a host to mate with them through direct skin contact, often enveloping itself around the host. Empath first encountered the Nocturnians when he noticed Papa Smurf was sleepwalking into a cave where he was being melded by a Nocturnian.