The Sullurh were a spacefaring humanoid race native to the Alpha or Beta Quadrants from the planet Kirlos. By the 2360s, the Sullurh had established contact with the K'Vin Hegemony and the United Federation of Planets.
Physiologically, the Sullurh were small-boned, pink-skinned, had heavy eyelids with large pinkish eyes, triangular ears, and had a mane of hair which crowned the head and ran down the spine. They had the ability to go unnoticed in certain situations, as if they blended in with their surroundings. Some other races pick on them for their supposed simplicity, or they just ignore them even if they are noticeable.
In actuality, they were descendants of the Ariantu, those that remained on Kirlos to watch it while the others withdrew. Staying behind led to inbreeding, making them shorter and having stumpy tails which are unlike their ancestors'. These stumps were removed during the enio'lo ceremony.
The enio'lo, which means "Those Who Stayed", assimilated into the societies that took over Kirlos and insinuated into their power structures. They still had their ancestor's ideals in mind, protecting Kirlos and waiting to return to power.
When the Ariantu came back, the Sullurh willingly caused terrorist attacks to rile up distrust between the Federation and the K'Vin so the Ariantu could take over again. But the Ariantu never planned to compensate the Sullurh for all they did.