Morbius was once a Time Lord of the first rank, but he became a ruthless dictator with millions of fanatical followers and admirers. He destroyed civilizations on numerous worlds - including the planet Karn, a couple of billion miles from Gallifrey - making him a notorious war criminal. Morbius was aware of the existence of the Elixir of Life, a substance supplied to the Time Lords by the Sisterhood of Karn for use in dire emergencies. Until Morbius, only the Sisterhood and the Time Lords knew of the Elixir, but Morbius brought an army to Karn and promised them immortality. Morbius and his rebels overran Karn, and the Sisterhood were only saved by the Time Lords' intervention. Morbius' attack became widely known, and therefore so did knowledge of the Elixir, forcing the Sisterhood to jealously guard their treasure. The Time Lords executed Morbius for his crimes on Karn, and many people came to the planet to witness the trial. Morbius' body was dispersed...but somehow, his brain survived.
Following Morbius' death, an underground Cult of Morbius sprang up. Among the members was the celebrated neurosurgeon Mehendri Solon, who kept Morbius' brain in a tank filled with a lurid green colloidal nutrient. The brain was connected to a membrane so that Morbius was able to speak. While others laughed at Solon's belief that he could create life, Morbius believed him, and Solon set out to prove Morbius right. After assembling a lab and conducting experiments, he built Morbius a new body. It was composed partly of a large claw, left human arm, and the lungs of a Birastrop with a methane filter. While this was going on, Morbius had developed a plan to outwit the Time Lords, yet he was paranoid that they would discover he was still alive and track him down.
Finally, Morbius' new body was almost ready - the only thing it lacked was the perfect head. Despite Solon's attempts, he was unable to secure one, and was forced to use a brain case that he had developed previously. It had never been perfected, however, and he feared that periodic jolts of electricity would build up in the case, causing pain and seizures. Morbius was adamant that the operation proceed as quickly as possible, and despite his brain being dropped on the floor at one point, the operation went off without a hitch.
Unfortunately, a combination of electrical shocks, trauma from being dropped, and gradual madness from being trapped in a tank without his senses had caused Morbius to go even more insane than he had once been. Following the operation, his brain began working at the instinctual level. As his deepest level of emotion was hatred for the Sisterhood, Morbius determined to destroy them and would not let anyone stop him. He attacked Solon in a rage, then went after the Doctor and Sarah, and throttled Solon's servant Condo. Solon chased Morbius outside and tranquillized him, then hoped to correct the imbalance. Unable to stop him, the Doctor was forced to mix a poisonous batch of cyanogen from hydrogen cyanide - one of the components of Morbius' colloidal nutrient - that he found in Solon's lab. The gas infiltrated Solon's operating room and killed him, but not before Morbius had been repaired. The creature's Birastrop lungs kept it alive, and it emerged to confront the Doctor.
The Doctor suggested that Morbius needed a new name for his new body, but neither Potpourri nor Chop-Suey went over well with the deranged creature. In a last-ditch attempt to defeat him, the Doctor challenged Morbius to a mind-bending contest. In this usually harmless Time Lord game, the players of the contest attempted to force one another back through their previous regenerations - but Morbius played to kill. Both Morbius and the Doctor were wounded in the attempt, and shortly thereafter the Sisterhood stormed Solon's castle, forced the dazed Morbius outside and backed him off a cliff.
