The Glory was the focal point of the omniverse. Whenever the Glory's controller was about to die, two rivals would be selected to fight for control of the Glory, and whoever won the duel would become the new controller of the Glory.
At one point, Esterath became controller of the Glory and kept it safe from all who would use it for evil.
Esterath grew weary and sought a successor. He found the Master floating in the Time Vortex and saved him. Esterath gave the Master a new body and told him that there would be a fight over the Glory. The victor would control the Glory itself.
The Master assumed that the battle would be between him and the Eighth Doctor. However, the Master was mistaken: the true battle was between his companion, Sato, and the Doctor's, the Cyberman Kroton. Kroton was the ultimate winner of this contest; His first acts as controller of the Glory were to heal the Doctor's injuries and then banish the Master into an apparently inescapable prison. (COMIC: The Glorious Dead)