Tanis was an Ocampa living on Suspiria's array who tempted Kes with her people's dormant mental powers.
Tanis was a member of an Ocampa colony that had left the homeworld centuries earlier with Suspiria, the female Nacene who served as their caretaker. Under her guidance, his people developed telepathic and telekinetic abilities far beyond those of Kes's community. Gary Graham played the role.
In Cold Fire, Tanis came aboard Voyager and offered to teach Kes, but her lessons nearly killed Tuvok and set the hydroponics bay alight. Tanis urged Kes to abandon Voyager and join his people, but he was also leading the crew to Suspiria, who believed lies about them and meant to destroy the ship. Kes ultimately rejected him.