McKraken has medium gray skin, eyes with red sclera and yellow irises, teeth with large canines, a shadow that is on his face, a large nose, and a white mustache. He wears a white robe with bronze colored studs and a round object resembling a porthole, a dome shaped white hat with black spheres on the side, and white shoes. What's notable of McKraken is his silver-gray tentacles which serve as his hair and beard and are curled at the end. Three of them are the beard and the rest are seen moving in the air.
In his second form, McKraken is more monstrous. His body is round, purple and silver in color, he has purple coloring in certain spots on his body, purple striped horns, eyes that have several rainbow colored spirals, and numerous tentacles on his back and even up his nose. Often, McKracken's body in his second form had another mouth with the inside having a red sphere.
McKraken has a deep contention with the human world and their denizens to a fervent degree. He also sees Yo-kai that side with humans to be pets and traitors.
As his bio in the Yo-kai Medallium states, McKraken can absorb energy through the suction cup-like holes on the palms of his hands and he can also cause marine disasters. Additionally, he was the one who created the White Yo-kai. He can control the elements in battle, and he gains the ability to use many Inspirits in his second form.
Before the events of the first game, McKraken seized control of the Yo-kai World after the death of King Enma. King Enma's heir was sent to Earth and raised as a human for eleven years while McKraken consolidated his power.
By the time of the first game, McKraken had begun to put into motion his true plan; conquest of not just the Yo-kai World, but the human world as well. He initially sends a Tengloom loyal to him to attempt to unleash Slimamander on Springdale, but is foiled by Nate/Katie. It can be presumed he was also behind sending Massiface to try and eliminate Kyubi, but the wily fox Yo-kai pits Nate/Katie against the giant, with the latter coming out victorious. Finally, in an attempt to rid himself of the human thorn in his side, McKraken sends Dr. Maddiman to lay a trap for them, but this is foiled as well.
McKracken finally decides to launch an all-out invasion of the human world, and is shortly after confronted by the Yo-kai that the protagonist befriended. After he is defeated, he warns them that he will always come back. Kyuubi later informs them that the Chairman disabled all the Yo-kai seals while they were fighting, thus causing the evil Yo-kai to escape to the human realm. This becomes evident when Slimamander returns and fights the heroes again. The heroes successfully beat it, but find out that Uptown Springdale is already taken over by Yo-kai faithful to McKraken.
Whisper suggests that their best bet is to seal all entrances to the Yo-kai World, including the Yo-kai Elevator. However, this will also mean that all Yo-kai the protagonist has made friends with will also be gone forever. Seeing as they have no other option they agree to with, Whisper gives the hero/heroine some Blossoming Powder and they use it to seal all of Uptown Springdale. Soon, the humans begin to notice a calmer aura surround them. They later track down the last rogue Yo-kai to the Sacred Tree. It turns out to be McKraken himself who, as a last stand, proceeds to absorb all the aura that channels through the Sacred Tree and become a powerful monstrosity. The heroes and all the Yo-kai that the protagonists befriended prepare for their final battle and finally defeat him for good. With Mckraken gone, heroes and all the Yo-Kai that the protagonists befriended sealed all entrances to Yo-kai World, including the Yo-kai Elevator in order to stop the evil Yo-kai's full-scale invasion on the human realm.
Besides the bosses that reside in the Infinite Inferno, McKracken is the only Boss Yo-kai to be rematch-enabled in the first game.
McKracken is the only boss that can be fought multiple times in the same day.