A rough and mocking attendant at the mental hospital on Tilonus IV in which Commander Riker believes himself confined in 2369.
Mavek appears in the episode Frame of Mind, played by Gary Werntz.
Riker finds himself slipping between two realities. In one he is acting in a play aboard the Enterprise-D, and in the other he is a patient in an alien asylum, accused of murder. Mavek is the ward attendant there. He mocks Riker's talk of a starship, calls him by a patient's name and is quick to use force and sedatives.
As the two worlds bleed into each other, Riker can no longer tell which is real, and Mavek's bullying adds to his fear that he is going mad. The truth is that Riker has been captured during a secret mission on Tilonus IV, and his captors are probing his mind. The asylum and its staff are images his own mind has built to defend itself.