For Institute of Occult Sciences
It may look cute but it's an omnipotent jerk
Lemurians are actual, literal lemurs. You can distinguish them from their common relatives by their perfectly white fur, their massive bioluminescent eyes, their intelligence, and of course their presence beneath the earth, a place which is otherwise pretty devoid of arboreal mammals.
Like the other root races of the underground, Lemurian civilization existed well before humans made their own descent (from the surface? from the treetops?), and is much diminished. Unlike the maggot-men or the polyps, they weren't undone by some great disaster or transformed into something else; they just turned their attention away from the physical world.
Lemurians have mastered the power of using information to manipulate reality. The principles they use to do this are similar to the lucid science studied at the institute, but in Lemurian hands the art more closely resembles reality-manipulation or psychic powers. They can rewrite genomic sequences, implant an idea in someone's head, conjure objects from nothing, and beam themselves through time. (In fact, many colonies skip across history like a strepsirrhinian Brigadoon).
The tool they use to do all this is their glowing eyes. Light is a medium for transmitting information, and to a practitioner of lucid science, this makes it something between a hand and a scalpel. Lemurians have a complex series of nictitating membranes that they can use to modulate the color and intensity of their eyeglow, and thereby form patterns that act upon the informational aspects of reality.
If that seems overly abstract, consider an analogy: A book has a physical aspect, which is made up of paper and ink, and an informational aspect, which is made up of words. If you could edit the informational component, replacing one paragraph with another, then this change would propagate to the paper and ink, which must now be arranged in a way that spells out different words. This is how Lemurians and lucid scientists are able to reconfigure material things.
To Lemurians, practical applications of these techniques are all very prosaic - not necessarily simple, but secondary to the more obscure philosophical studies they pursue in abstract space.
Lemurian colonies are miniature jungles. The trees are bone-white, like the Lemurians themselves, and have hollow interiors which can be used as shelter or to store small objects. Lemurians have few personal possessions, but they do collect food, jewelry, scrolls, and art objects.
(The trees are bioengineered, resembling surface flora in form but not in function. While the underground does have plants, no sunlight means no photosynthesis, and no reason for anything to evolve in the shape of a tree. Instead plants get nutrients from parasitism, carnivory, tidal effluvia, and a collection of deeply weird transmutative processes that verdant science has yet to figure out).
These places are always eerily silent. Lemurians move very quietly, and they communicate by staring into their interlocutors' eyes and projecting thoughts telepathically. The only time they make noise is when they're in pain.
In the center of the colony there will be structures made of transparent crystal, usually in the shape of organic whorls, arches, and spires. The configuration of these crystals reflects the structure of abstract space, containing definitions of the colony that can be used to hide it from the perception of outsiders or shunt it forward in time.
Lemurians are meddlesome, and they don't seem to think of humans as real people. They might offer some scraps of technology in exchange for services rendered, but they're just as likely to play outsiders against each other, embed hypnotic suggestions in your mind, or erase an inconvenient visitor from reality.
It's unclear how this squares with their habit of adopting human children. These foundlings are given Lemurian eyes, treated almost as a member of the colony, sometimes even taught a little informational magic, but then abandoned when it's time for the lemurs to move on.
