A slave species of the Romulans.
The Remans are a pale, bat-like humanoid species from Remus, the twin world of Romulus. Remus is tidally locked, so one side of the planet is always dark, and the Remans live in that darkness and are sensitive to bright light. They also have telepathic abilities.
For generations the Romulans treated the Remans as an underclass, forcing them to work in the dilithium mines of Remus and using them as shock troops in wars. In Star Trek: Nemesis, set in 2379, Shinzon, a human clone of Picard who had been sent to Remus as a child, rises to lead the Remans. He and his Reman followers wipe out the Romulan Senate and take control of the Empire.
Shinzon's chief ally is a Reman known only as the Viceroy, who uses his telepathy to invade Deanna Troi's mind. The Remans crew Shinzon's warship, the Scimitar, which is destroyed in the battle with the Enterprise-E.