The Gray Tiger was a Behemoth-class battlecruiser.
After the Brood War, Gray Tiger was in service with the Terran Dominion under the command of Captain Robert Mason. The ship ferried four archeological teams to Nemaka to investigate a xel'naga artifact. The fourth team under Jake Ramsey was successful but they were eventually brought back on board and imprisoned pending interrogation. The team escaped after undoing Marcus Wright's neural resocialization. The marine rampaged through the ship and destroyed its life support system, eventually killing all those unable to escape.
The derelict ship was eventually discovered by Admiral Hector Santiago and Valerian Mengsk was briefed on what had transpired. Gray Tiger, which was over seven years old at this point, was ordered destroyed as a result.