S'glhuoans are a sapient extradimensional species native to a realm in which sound manifests as matter, and matter manifests as something akin to odors. As such, the S'glhuoans themselves, like every material thing from their native dimension, are made of sound.
The natives of the realm known as the Gulf of S'glhuo are sound-based creatures which can only manifest as sounds in the material universe; just like sound itself can manifest as matter in theirs. They can somehow communicate with other creatures in dreams, even across the universes.
Their natural form resembles a tall, thin, reptilian humanoid with blue squamous skin, tentacular fingers, and huge white eyes without pupils. Their boneless fingers can extend up to 60 cm, and they've been observed to behave in a curious way by gathering in circles, extending their fingers towards the center of the circle and interlacing them. It's been speculated that interlacing fingers might be a form of communication among members of this species.
- "The Plain of Sound", by Ramsey Campbell (1964)