Morbius

Morbius is a notorious criminal Time Lord and the main antagonist of Season 4.

Role
Morbius is first seen at the beginning of Season 4, where he is nothing more than a brain in a jar. He is given a new body in the third episode of the season by the Ninth Doctor who has been paid to work for him. This new body has the lungs of a Birastrop, allowing him to breathe in toxic gases and a giant claw on his right arm. His left arm has a human hand. His head is a plastic brain case due to General Staal's head not being suitable.

Morbius proves to be a very hard adversary to kill, being able to survive an explosion which Brannigan set off to kill him (along with himself) and taking out a small squad of Cybermen.

In the last 2 episodes of Season 4, he forms an alliance with the Ninth Doctor, General Staal and Omega, calling his team "Stormageddon" to take part in a "Survivor" style tournament to locate the Fifth Doctor. Ultimately, his team fails due to Team Coolio (The Eleventh Doctor, the Fourth Doctor, Sclar and Ood Sigma) finding the Fifth Doctor first. Enraged, Morbius gets everyone to vote a dead General Staal off and then finds another secret weapon: A Giant robot!

Morbius uses the Giant Robot to find a Cyberking to conquer the Universe with, crushing many people under the robot's massive feet in the process. However, the Fourth Doctor manages to reprogram the robot so that he protects man instead of harming it and use some of the TARDIS' energy to make him grow as big as the Cyberking. Once the robot uses a virus to kill himself and the Cyberking, Morbius falls of the Cyberking to his death.