Erogenetians, also known as shaftbeasts, are a monster species created by TwilightMaster. Erogenetians typically fit under the penis creature umbrella, possessing phallic-shaped appendages, unusually-shaped body parts or otherwise exaggerated sexual features. Their faces are notably eyeless and often phallic-shaped, and they typically possess a set of "antennae" which can appear anywhere on their body.

The term shaftbeast is usually used to refer to the general species, with erogenetian being their name used in sci-fi canons. Members of the species possess mental links they can communicate with, with particularly close-linked clusters of erogenetians being referred to as broods. Each erogenetian is also a shapeshifter, able to take on shapes more reminiscent of other species as means of diplomacy or blending in to the local cultures.