A humanoid species with strong telepathic powers, able to launch a mental attack that can leave a victim's mind trapped in a coma.
The Letheans are humanoids known for powerful telepathic abilities, which they can use as a weapon.
In Distant Voices, a Lethean named Altovar attacked Julian Bashir after Bashir refused to sell him a restricted biomimetic compound. The telepathic attack trapped Bashir inside his own mind, where he aged rapidly and found aspects of his personality taking the shape of his crewmates. Bashir fought his way out of the illusion and recovered.