It was almost a relief when he was shot again, this time by a guard who had decided to be a hero. All those goody two-shoes feelings gone, he was free to be back to his usual self. It was with great delight that he murdered the man, ripping him to shreds with his bare hands.
All was not right with the Master though, as he learned in the coming days. Something had gone wrong with this regeneration. His past incarnations, usually dormant memories in his head, were now crowding his every thought, pulling him in every direction. Every version of him, from both his regeneration cycles, from all the times he tried to escape death, they all started to scream at him and try to take control of his mind. As he struggled to stay in control he realized why Rassalion had put the twelve-regeneration limit on the Time Lords in the first place. Live too long, and even a Gallifreyan mind struggles to keep itself together. He tried to keep his cool, but often meetings with his underlings were interrupted with his madness. It was almost as if his head was going to explode!