Garrick was a tall and scarred terran marine. He had been on Revera where 800 lives were lost in a day, there he almost lost his leg to a queen. He also had a groove on his skull caused by friendly fire.
He was assigned to a world threatened by the Zerg Swarm along with Charn, Prescott and Kort. Their orders were to wait until the swarm arrived, then a ghost would call in a nuclear strike and give them orders as to when to evacuate. When their ghost contact failed to communicate they agreed one of them would go out of their bunker to find out if he was still alive.
They played a card game to decide who, where Prescott lost. However, Charn revealed that Garrick was using an extra nine of diamonds. Garrick went berserk, saying he had served in enough battles and that he refused to do anymore. Charn volunteered to go in his place.
McAleese, Danny. "The Exit." (July 1, 2014). Blizzard Entertainment. StarCraft Lore: The Exit Accessed 2014-07-02