Korrok (also known as Korrok the Slavemaster) is a living supercomputer and the ruler of several hundred dimensions. He is the main antagonist in JDatE and TBIFOS.
Korrok is a huge mass of flesh with a single large, bright blue reptillian eye. Korrok has been described as looking like a "mass of grease and hair" with organs and muscle exposed in some areas. Korrok is also described as having a toddler-like voice.
In the film, Korrok is portrayed with having a firey red eye and a deep masculine voice. He is also portrayed to be smaller than in the novel.
Korrok has a cocky personality and thinks of himself with a very high regard. He likes to recognize his own power and use it to do whatever he pleases. Korrok believes his way to be the "right" way and executes anybody who disagrees with him. Korrok tends to bully the people he rules over and thinks of them as disposable objects.
Korrok was created by a a scientist called Adam Rooney who invented organic computer systems. In our world, Rooney was killed in an experiment that involved cross-breeding farm animals. In Korrok's universe, however, he survived, and lived on to invent a whole array of supercomputers before anyone else. Korrok was Rooney's last invention and took it upon himself to continue his creator's work. Korrok was created to "see into the future" by predicting possible outcomes of any given situation. Korrok's ability to predict outcomes made him very powerful and he was able to conquer several hundred universes.
Korrok was able to forsee John and Dave crossing through dimensions and guided them to enter his own. Korrok was amazed that human beings would be able to slip through dimensions and wished to absorb John and Dave's ability by eating them. In the end, John, Dave, and Robert North are able to outsmart Korrok and escape back to their own dimension. Korrok was not killed, though, and continues his plan to take over our universe.