Death on Elba II (Mirror Universe)

Inviting Captain Spock to a lavish ceremony in his honor on Elba II to promote him to Admiral, Grand Admiral Garth correctly deduced that his rise to power was the result of an alien weapon which he had taken from his predecessor Captain James T. Kirk. Using the shape-shifting techniques that he had learned on Antos IV many years before, Garth hoped to beam onto the ISS Enterprise in Spock's form and claim the weapon for himself. He would then use it to kill Admiral Spock and his wife Commander Marlena Moreau before turning it against the Empress and declaring himself Emperor. However, Admiral Spock - having learned of Garth's ability from Kirk's records - anticipated this move, developing a chess-related code, which foiled Garth's attempt. Infuriated, Garth opened a channel to his flagship, the ISS Imperious, to destroy the Enterprise. However, Marlena killed him using the Tantalus field before he could give that order. His Orion mistress Marta suffered the same fate almost immediately afterwards. Garth's successor as Grand Admiral of the Imperial Starfleet was Matthew Brand Decker of the ISS Constellation NCC-1017, who served in that position until being killed by Spock in 2277.