Groff was from Xaranor, a Federation planet specialising in constructing and crewing survey ships. He had a wife and two children there.
Groff's vessel was in Sector 12 when it was drawn down to Crandor. Groff became resigned to his fate as a slave of the Thaarn and within only a short period of time had risen to the post of senior technician. (Groff knew of the Liberator and so couldn't have been a prisoner for more than a few years.) For reasons best known to himself he dressed as an archaic croupier, in shirt, vest, and tinted visor.
Although having been promised the rule of his own planet when the Thaarn conquered the universe, Groff quickly agreed to help Avon and Tarrant when they were brought in. Groff told them the information they needed to plan their escape. When the energy isolators were switched off, it was Groff who reversed the gravity generator and grappled with the Caliph of Crandor while the others escaped. He asked only that the Liberator take a message to his family, that they were always in his thoughts.
Groff was killed when the reversal of the gravity generator caused the destruction of Crandor.