The Letheans (Second Human Empire: ?) are a telepathic species from the Duyi'zu Universe, whose telepathic attacks are almost always fatal, not even a Jedi. Their skills led them to being hired by various criminal groups in the 24th century Duyizu. They are known for being incredibly stubborn.
In 2371, a Lethean named Altovar attempted to acquire a few hundred milliliters of bio-mimetic gel from Julian Bashir. After Bashir refused to give him the gel, Altovar telepathically attacked him, placing him in a coma. Altovar didn't get very far until he was arrested by Odo.
Letheans are bald, with a vertical bone ridge that runs across their face and heads. They have small bone protrusions that can grow along this ridge and on their cheeks, and their skin is mottled and has multiple cartilage folds. Their eyes have a reddish tint. Letheans are descended from reptiles and prefer the dark.