Black Fire was a legend of piracy that originated as the alias of a pirate force based on the planet Corsair in the year 2270. In actuality, the person most often thought to be "Black Fire" was Spock, who was operating as a pirate in a sting operation. The alias was also used, for the purpose of misdirection, by Spock's partner in this venture, Desus.
Spock and Desus acquired a pair of identical Starfleet cruisers and, along the same lines of misdirection, marked both vessels with the name Black Fire, although in actuality they used their own names for the vessels, the Talon and the Equus. (TOS novel: Black Fire)