A Xindi-Primate who serves aboard Degra's ship and is captured with him by Enterprise, then returned with his memory erased after Archer's elaborate deception.
Thalen appears in the Enterprise episode Stratagem. He is a Xindi-Primate member of the crew of the vessel carrying Degra, the scientist designing the weapon intended to destroy Earth.
Enterprise disables the ship and takes its crew prisoner. While Jonathan Archer stages an escape in a simulated shuttle to trick Degra into revealing where the weapon is being built, Thalen and the others are held unconscious in sickbay.
Once Archer has the coordinates of Azati Prime, Phlox removes the prisoners' recent memories. Thalen and Degra are put back aboard their ship, with evidence arranged to suggest they had merely been drinking, and left with no recollection of the encounter.