War Master

This incarnation of the Master presumably escaped the Time War and hid at the end of the universe. However there could have been more than one form involved.

Biography
The Master was resurrected by the Time Lords during the Last Great Time War. They believed that he would be a perfect warrior for the Time War. He was present when the Dalek Emperor took control of the Cruciform. Frightened by the horror of the Time War, he ran away to the end of the universe. There, he used a chameleon arch to hide himself as a human, Professor Yana. Years later, Martha Jones helped the Professor notice his fob watch, despite the perception filter. The Master had false memories. When Martha Jones asked how he had got his fob watch, he claimed he had it when he was washed up on a beach as a child. He opened it and became the Master again. His human name, Yana, was an acronym for "You Are Not Alone", the final words of the Face of Boe. The Master allowed the Futurekind to enter the silo. He attacked Yana's assistant Chantho when she stood in his way. Chantho shot him before she died. The Master then entered the safety of the Doctor's TARDIS and regenerated into his next incarnation, stating, "If the Doctor can be young and strong, then so can I. The Master reborn!" (DW: Utopia)

Personality
This incarnation's personality was cold, ruthless and vengeful, a contrast from his human form. In contrast to his next incarnation, he was always serious and dignified. (DW: Utopia)