Glass Empires storylineEdit
Designed as a wargame simulator for the Imperial Starfleet of the Terran Empire, it was put in command of the ISS Excalibur in 2268. In this wargame, it faced off against the ISS Enterprise, ISS Lexington, ISS Potemkin and ISS Hood. However, when it was supposed to use low-powered phasers, it instead fired on the other ships at full power, destroying the Potemkin and nearly destroying the Enterprise. Using an unorthodox strategy, the Enterprise's captain Spock and his first officer, Montgomery Scott, brought up the datacharts of the command consoles of the other two fully-crewed ships, knowing that M-5 would have changed the prefix codes of Excalibur to prevent what he was about to attempt. He armed the self-destruct package of both the Lexington and the Hood and detonated them when they were in close proximity to the Excalibur, vaporizing all three ships.
The incident was reported to Starfleet Command as an accident but Spock correctly believed that it was an attempt to assassinate him by his enemies in Starfleet. Dr. Daystrom had assured Commodore Robert Wesley, captain of the Lexington, that his creation could indeed destroy the Enterprise, but had not brought up the possibility that it would turn on them as well. Wesley would pay for that mistake with his life. (TOS - Mirror Universe novel: The Sorrows of Empire)
Shattered Universe storylineEdit
An M-5 Unit was created by the Terran Empire who abandoned it in an old weapon testing range in space where it managed to take control over four derelict Constitution-class vessels. Its territory was intruded upon by the ISS Excelsior's whose crew had exchanged places with their primary universe counterparts as a result of exposure to the Janus Vortex. After attempting to trick the computer, Captain Hikaru Sulu had to fight the fleet assembled by the machine who attempted to protect itself from destruction. Its intelligence was located on the ISS Hood which was destroyed by fighter squadrons from the Excelsior which ended the threat posed by the machine. (TOS video game: Shattered Universe)
- "M-5 readout. Lifeform readings recorded. Lifeforms must be neutralized."
- "This unit must survive."