Aborted regeneration

From Tardis Wiki, the free Doctor Who reference

After being gunned down by the War Lords, the War Chief underwent an aborted regeneration which he attributed to his "massive injuries, the extensive tissue damage, the complete lack of all medical care". This left the War Chief in a half-regenerated form resembling two bodies grotesquely fused together. His torso, which required extensive bandages, sprouting "twisted" stubs of extra limbs, and his head had a second, incomplete skull growing from the back of it, giving it an odd, enlarged shape.

Adopting the name Felix Kriegslieter as he operated on Earth, the War Chief was confronted by the Seventh Doctor and Ace. In the final moments before his base at Drachensberg castle collapsed, Ace briefly glimpsed the War Chief engulfed in flames. With the new deadly injuries having seemingly reset his regeneration, he appeared healthy once more — "young, tall, dark and satanically handsome". (PROSE: Timewyrm: Exodus) Some accounts suggested that the Time Lord who had acted as the War Chief during the War Games incident had subsequently become the Master who menaced the Third Doctor during his exile on Earth, (PROSE: Doctor Who and the Doomsday Weapon, etc.) although during his encounter with Kriegslieter, the Seventh Doctor seemed to believe that he had not encountered the War Chief since the War Games incident. (PROSE: Timewyrm: Exodus)