The Master (John Simm)

Overview/History:
The Master is a renegade Time Lord who had stared into the Untempered Schism and gone mad because of it. Rassilon the president of the Time Lords instilled a tracking device made out of a consecutive number of drum beats in order for those old gods to escape the Time War and make Earth into a brand new Gallifrey which is the old home planet of the Time Lords that got destroyed by the Daleks The Master however stopped Rassilon at the seemingly massive cost of his own existence trapping them back at the end of the war.

Pre Time Lord Revolution:
Before Rassilon's master plan however The Master being a man of disguise took the name of Professor Yana and stranded himself on Macassario who's occupants were planning to board a non functional rocket towards Utopia so when the Tenth Doctor, Captain Jack Harkness and Martha Jones landed on Macassario The Doctor helped everyone get onto the rocket which was step one in The Master's plan, albeit he didn't know it was because his Fob Watch which stored the Master inside by use of a Chameleon Arch provided a perception filter Officially Yana was born in the Silver Devastation and was just a scientist trying to get everyone to Utopia but ultimately it was to lead them all to death and a gruesome transformation. Once his plan was achieved he travelled to 21st Century, London, England and started to run for the position of Prime Minister which he eventually won. He even met and married Lucy Saxon and brought in the Toclafane which was apparently the final form of the human race. However Prime Minister "Saxon" would be defeated and killed by his wife despite the Doctor's pleas to have him regenerate.

Regeneration?
The Master comes back due to his cult followers remembering The Year That Never Was but it went horribly wrong due to yet again his ex wife Lucy. He was on the brink of death with superpowers like Electricity Manipulation using Artron Energy that would normally be stored in a TARDIS or the Time Vortex He created a species known as The Master Race which all were exactly like him down to the smallest detail.

The Incoming Revolution:
The Time Lords used the Immortality Gate as their point of entry when they escaped the war and confronted the two children of Gallifrey and when The Master finally saw what could happen he turned on the President and severed their link to Earth but he took himself with them seemingly causing his end.

Return:
He returned to life again taking another disguise and interacting with his female incarnation Missy and had a alliance against the Twelfth Doctor but he died yet again along with Missy.

Powers and Abilities:
Can regenerate after death and take over bodies

Amazing intelligence

Telepathic and hypnotic abilities

Advanced time and space travel related technologies - in possession of a deadly laser-screwdriver

Able to jump very high and to shoot lightning out of his hands after his resurrection

Canon:
The Master in his Harold Saxon form worked with and for groups like HYDRA and Le Paradox's Gang and he had not had many appearances until one faithful day when he was assigned to defend a HYDRA Storage Facility along with Alexander Paine and Mr Kelly. S.H.I.E.L.D. however staged an assault and blew up the building killing the three villains along with numerous soldiers.

Non Canon:
In Thor and Loki go to Asgard he along with HYDRA tried attacking them along with the Thirteenth Doctor and got captured in the process. It was revealed however that Chameleon was impersonating him