Thelev
Thelev was an Orion posing as a member of the Andorian delegation at the Babel Conference. ()

Biography 
Serving as an aide to Ambassador Shras, Thelev's mission was to destroy the , which was responsible for transporting delegates to the Babel Conference. The purpose was to instigate mutual suspicion and possibly interplanetary war. Had war broken out, the Orions would have cleaned up supplying dilithium to both sides while continuing to raid Coridanite.

He murdered the Tellarite ambassador Gav by breaking his neck and later tried to murder James T. Kirk with a knife. He managed to stab Kirk but was captured and put in the brig. When he tried to escape he was stunned with a phaser and fell so that one of his e broke off and revealed a hidden device he had used to communicate with his ship. When Enterprise damaged his ship, it self-destructed and Thelev took a poison that killed him. ()

Appendices

Background information 
Thelev was played by actor William O'Connell and by stunt double Jim Sheppard. Sheppard's appearance as Thelev can be clearly seen with Caucasian flesh-colored hands.

Apocrypha 
The TOS timeline in the novel  picks up immediately after "" and states that the knife Thelev used against Kirk was poisoned. Leonard McCoy treated the wound but it continued to pain Kirk for decades afterwards.

External link 
 

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Aliases
Orions