If you are looking for poo, go and shit at your loo (it rimes, yay!).
The Shadow Blot (his name is often confused with the name of the Phantom Blot) is the main villain in Epic Mickey, and acts as its Final Boss (though that is up to interpretation). He is a mixture of Paint and Thinner.
A long time ago, Mickey Mouse discovered, inadvertently, the workshop of Yen Sid, where the sorcerer was finishing creating a world where his lost and forgotten creations would feel at home. However, after waiting for Yen Sid to leave, Mickey takes a closer look at the model of said world, where he uses a paintbrush to create a small model of himself. The model turns black and melts slightly, so Mickey, believing more paint will make it more lively, keeps making it bigger and bigger... until it forms into the Shadow Blot, a demonic monstrosity who tries to attack Mickey, but the mouse accidentally spills paint on the model and grabs a sponge and splashes the Blot with thinner, seemingly erasing the beast. Hearing Yen Sid approaching, Mickey tries to cleans up (in vain) and accidently knocks over the paint thinner escapes through the magic mirror to home, believing this will all just be a silly memory. Unfortunately, part of the Blot was still in the sponge, and it escapes through a portal into the world Yen Sid created, where he usurps the throne of Oswald the Lucky Rabbit, and the Blot Wars engage...
A disconnected under the same name, is the secret ruler of the wasteland, its figurehead being the real Shadow Blot, its lookalike, and is making the lives of the residents of Wasteland so miserable, that they are trying to escape by attempting to steal Mickey's heart. Mickey must now face the monster he created to right all his wrongs... or make them worse...
After defeating the fake Shadow Blot at Mickeyjunk Mountain, Mickey and Gus rush to the mountain's peak to help Oswald seal the blot in the Jug. There Oswald reveals that the Blot they fought was just a very big drip from the Shadow Blot. He tells them that when the Blot first arrived, he and Ortensia managed to seal it in the Jug, but Ortensia was lost in the process. Oswald then asks Mickey to be friends, but before they could shake hands, Mickey sadly reveals that he was the cause of the Thinner Disaster. This greatly enrages Oswald, who jumps on the Jug's cork, ready to fight Mickey. However, as he moves, the cork begins to crack, and bursts open, freeing the Shadow Blot. The Blot promptly grabs Oswald and Gus and demands that Mickey surrenders his heart. Not wanting his friends to die from either not having the ability to breath, or that the Blot would crush them, Mickey grudgingly agrees. Now energized with Mickey's heart, the Blot creates his bloticles and begins to drain all of the paint out of the wasteland.
Mickey and Gus manage to destroy the bloticles, while Oswald fixed the rocket. Once all the bloticles were destroyed, they decide to use the rocket to reach the Shadow Blot and use the rocket's self destruct feature near Mickey's heart. However, the Blot uses its bloticles to destroy the rocket (as it was made of paint due to budget issues). The Rocket crashes into Dark Beauty Castle. Luckily, Oswald has a plan B: launch three sets of fireworks at the Blot. Mickey manages to activate all three fireworks sets while Oswald distracts the Blot, but just as they are ready to launch them, the Shadow Blot swallows Oswald and Gus, forcing Mickey to jump into the Blot to save them, while inside the Blot, Mickey reunites with Gus, and they find Mickey's heart, where it's revealed that once the Blot regains its strength, it will use Mickey's heart to enter his world. Mickey manages to free his heart by destroying the bloticles holding it suspended. Oswald grabs Mickey's heart, but after a brief hesitation, willingly gives it to Mickey. Oswald then activates the fireworks, destroying the Blot once and for all.
The Shadow Blot isn't fought directly, Rather you fight parts of him. These parts are called Bloticles, and they are in every hub world in the game, Mean Street included. The tentacles will frequently grow boils, and Mickey must use Thinner or Paint (it doesn't matter which) on these boils in order to destroy them. Continue doing this to every Bloticle in every hub world to initiate the last two phases of the triumphant fight to the finish. While the Bloticles absorb all the Paint in whichever hub world they are in, this does give you an advantage to find all of the hidden areas the Paint previously had covered up.
Oswald has another plan: Using the castle's fireworks to defeat the Blot. But in order to do so, the fireworks on each tower must be activated. To activate a set of fireworks, Mickey must activate the tower's three gargoyles by spinning them so they will face the floating crystal in the center, and painting the faces to activate them. But Mickey must beware as the Blot will attack him with its claws while he does so, and he can deal heavy damage. After activating all three fireworks sets, The stage is set for the final showdown.
Inside the Blot
The Blot has swallowed Oswald and Gus, forcing Mickey to venture into the Blot to save them. Upon venturing deeper into the Blot, Mickey reunites with Gus and they discover Mickey's heart and realize the Blot plans to use Mickey's heart to enter his world once it regains its strength. To defeat the Blot, Mickey must destroy all four bloticles suspending Mickey's heart. This is similar to the previous battles in the hub worlds, but now you face dark remains of characters who were consumed by the Blot. These new enemies cannot be defeated, but will die when a bloticle is destroyed. Once all four bloticles are destroyed, the Blot will be defeated once and for all.
The Blot was originally supposed to be officially named Phantom Blot, like in the 1930's comic (which ended up being the fake Shadow Blot's fan-moniker). That idea stayed the same. But some ideas were scrapped. The Shadow Blot was supposed to be larger and was supposed to have glowing red eyes instead of glowing green ones. He was also meant to have a somewhat skeletal face and a sort of Horned King-like look as well, which would've made Epic Mickey a much darker game then it was.