The Master is a Time Lord and arch-nemesis of the Doctor. He tries many nefarious deeds and alliances to try and kill the Doctor, including allying himself with the the Autons and the Daleks, and also attempting to transform all humans into duplicates of him and trying to crash assorted large objects into the planet.
The Master is insane, and is constantly tormented by a drum noise in his head. He blames his insanity on the constant rhythm, and tries everything he can to stop it. he thinks killing the Doctor is somehow the key to finally ending the constant sound of drums.
The Master and the Third Doctor shared a bitter rivalry when they were both trapped on Earth. The Third Doctor had been exiled there by his own people and the Master arrived on Earth to challenge him, however, the Third Doctor disabled the Master's TARDIS so he too was stranded on Earth. The two masterminds battled it out using Humans as pawns in their war, and the Master used Autons, Daleks and Axons to attempt to conquer the Earth. When the Third Doctor was at last freed from Earth, the Master escaped soon afterwards.Rassilon to unleash hundreds of evil creatures onto the Galaxy. The Master also teamed up with the Rani to fight to Sixth and Seventh Doctors before disappearing completely...
It turned out that the Master had been captured by the Daleks and was put on trial for abandoning their alliance when he was freed from Earth. After being executed, the Master was transported to Earth by the Seventh Doctor but his remains possessed the TARDIS and caused it to land in a gang gunfight, causing the Doctor to be shot and killed as he exited the TARDIS. After regenerating and battling the Eight Doctor, the Master was destroyed by the Eye of Harmony, the power source for the TARDIS.However, this was not the end of the Master. When the Time War began, the Time Lords resurrected the Master to fight in the war but he instead fled to the end of the universe and therefore escaped the apparent destruction of his people.
The Face of Boe predicted the Master's return from the Time War, an eternal war between the Daleks and the Time Lords that was locked out of time, and only Dalek Caan was able to enter it, and it cost him his mind. The Master unwittingly transformed into a human called Yana, who was nice anf friendly until he opened the watch continaing the Master's soul, then the Master was reborn. The Face used his last breath to predict this, saying to the Doctor 'You Are Not Alone' (YANA), hinting at the old man's true identity. After taking over the world and imprisoning his foe the Doctor, the Master was finally defeated when the Human Race rose up against him. He was shot and killed by his wife and his body was burnt by the Doctor.However, the Master once again resurrected himself using the Cult of Saxon, a Cult set up to free the Master from death using the same technology that the Time Lords used to resurrect him in the first place. His resurrection went wrong, however, and he was forced to absorb his followers and kill them all just to survive. The botched resurrection gave him strange powers and intensified the drum beat in his head, which was actually a plot by the Time Lords all along. The beat in his head was a link that the Time Lords could use to escape the Time War.
The Master knew where his loyalties truly lay, however, when the insane leader of the Time Lords, Rassilon, was brought back to Life. He is revealed to be the one responsible for the Drumming, as it is all part of his plan to bring Gallifrey, the planet of the Time Lords, back to full might by using humans as slaves.
The Master is not too happy about this, however, and beats Rassilon up with his newfound powers, saving the Doctor but trapping himself in the process. Strangely enough, he was able to somehow escape Gallifrey and came back as a woman called Missy, who teamed up with the Cybermen in a very confusing sequence of events that no-one really wants to remember.
It is likely that, had they ever met, The Master and Jorgey would have got on very well.
The many demonstrations of insanity from the Master.