War Master
The Master was ressurected by the Time Lords during the Last Great Time War. He was ressurected because they believed that he would be a perfect soldier for the Time War, he was assigned to protect the cruciform. When the Dalek Emperor took control of the Cruciform he became scared and ran away to the end of the universe, using a chameleon arch to hide himself as the human Professor Yana. Years later, Martha Jones helped the Professor to notice his fobwatch, despite the perception filter, and he opened it, becoming the Master again. We find out that his human name Yana stands for " You Are Not Alone" the face of Bo's final words. The Master allowed the Futurekind to enter the silo and kill all of the Humans inside, he attacked Yana's assistant, Chantho when she stood in his way. Chantho shot him before he she died, the Master then entered the safety of the Doctor's TARDIS and regenerated into his next incarnation. Saying " if The Doctor can be young and strong than so can I, The Master reborn"
