Morbius

Morbius of House Dvora was a high-ranking Time Lord whose career was the first in milennia to dramatically alter Gallifrey's relationship to the wider universe, briefly moving the world's policy away from observation and manipulation of external affairs and instead towards brutal restructuring of the universe to suit Gallifrey's best interests (DW:The Brain of Morbius, FP:The Book of the War). The Fifth Doctor became embroilled in the chaos that resulted (PDA:''Warmonger). His career ended in ignominy and destruction, and he escaped a sentence of death only by means of a secret brain transplant, subsequent to which he encountered the Fourth Doctor (DW:''The Brain of Morbius).

The Imperator Crisis
Morbius' ambition led him to become the head of the High Council, where his warlike nature led him to urge the Time Lords toward a policy of conquest (DW: The Brain of Morbius), demanding the Laws of Time and structure of the universe be redrawn to better suit Gallifrey's needs (FP: The Book of the War).

While still based on Gallifrey he formed a personal army composed of both dedicated followers and mercenaries from other species. He promised these followers the secrets of time travel and immortality (DW: The Brain of Morbius) although withheld from them true admission into his House (FP: The Book of the War).

When the Time Lords, spurred by the Order of the Weal (FP: The Book of the War), eventually denounced him, he and his followers abandoned Gallifrey and began an assault on the cultures of the external universe (DW: The Brain of Morbius).

As Gallifrey's society struggled to understand these inconcievable events, the long-term cultural changes brought about would include the increased influence of the Celestial Intervention Agency and the founding of House Paradox (FP: The Book of the War).

War with The Alliance
Unsure how to respond to the physical campaign of conquest Morbius was waging against the universe (FP: The Book of the War) the Time Lords eventually chose to fight the war by proxy (PDA: Warmonger).

The Fifth Doctor, who had travelled into Gallifrey's past, was appointed 'Supreme Coordinator of the Alliance Battle Fleet' and directed an unlikey army of Humans, Draconians, Cybermen, Ogrons, Ice Warriors and Sontarans against Morbius.

Defeated with the assistance of the Sisterhood and brought to trial on Karn, Morbius was sentenced to be executed by disintegration for his crimes (PDA: Warmonger).

His body was indeed destroyed, with Sisterhood leader Maren in attendance. However, Morbius escaped death when one of his followers, the human surgeon Dr. Mehendri Solon secretly removed the Gallifreyan criminal's brain before his disintegration. Solon took the brain and went into hiding on Karn, where he began planning to build a new body for Morbius out of parts salvaged from corpses found in the wreckage of spacecraft which the Sisterhood had caused to crash on the planet as their way of protecting the Elixir (DW: The Brain of Morbius).

The Brain of Morbius
The Doctor and Sarah Jane Smith landed on Karn and stumbled upon Solon's castle just as Solon was completing Morbius' new body, leading them to discover Morbius. Although the Doctor had not previously met Morbius in person, he did recognize Morbius' telepathic brain pattern.

Morbius's new body was horrifyingly grotesque, leading the Doctor to mock him as "Chop Suey, the Galactic Emperor!" But Solon's ability to merge alien tissues together did give Morbius at least a few advantages over his previous biological form, including lungs from a Birastrop capable of withstanding cyanide. Other parts of Morbius' body included a human left hand which came from Solon's unknowing assistant Condo, a giant lobster-like right hand, and a humanoid torso. The body Solon had built lacked one important element, namely a head suitable for storing the unique and delicate properties of a Time Lord brain. Solon required the head of another Time Lord in order to safely house Morbius' brain, but when plans to use the Doctor's head failed and the container holding the brain was spilled, he resorted to an unproven, experimental braincase which included two stalklike eyes.

This braincase was prone to developing a static charge, a weakness exploited by the Doctor by challenging Morbius to a Time Lord mindbending contest. It is not at all clear who won the contest, but it was costly for both Gallifreyans. The Doctor collapsed from the strain, and Morbius' brain appeared to be damaged by a static shock. During the contest, images of the Doctor's previous three incarnations appeared in the air above them, as well as a number of images of others whose identity is disputed. It is possible that the unknown faces belong to previous and otherwise unexplained incarnations of the Doctor, suggesting that the incarnation known as the First Doctor was not, in fact, his first incarnation. However, it is also possible that the faces belong to previous regenerations of Morbius -- or that they are memories of entirely different people drawn from the minds of either the Doctor or Morbius.

After the battle, Morbius appeared to be left in a dazed, animalistic state. He did not speak again during the story, and only uttered seemingly agonized sounds of anger and pain. Leaving Solon's castle, he was chased by the Sisterhood over a cliff, where he was apparently killed.