First Bowser and then the fair Princess Peach were lost to the halls of Castle Bleck. Would they ever be seen again? Without his allies, could our hero Mario hope to stand against the evil Count Bleck? The very air in the castle grew heavier and even more ominous with every step. All they could do was plod forward in silence...
In Castle Bleck's Interior, Tippi notes the power of The Void is growing and the Chaos Heart is close. The end is almost here. There are flipping Skellobits here, some with spikes. The item blocks have a Happy Flower, Pal Pills, and a Slow Flower. There are also Cursyas. Go through the doors and you'll find Hogarithms. The door to the right doesn't work, so walk to the left of it and Super Jump up to a Sobarribad, a stronger version of a Barribad. Flip to get past the barrier to attack it. Now the door works.
This leads to a hall of mirrors with Dimentio appearing in them, along with many gaps in the floor. There are Longadiles here. Keep an eye on the mirrors, as one will not have Dimentio's reflection and will not shine. Flip and you'll be able to jump through it, as it's actually a window. There's a chest at either end of this room, one with an Ice Storm and another with a key. Go back through the window and unlock the door on the right. The door leads to some stairs. Flip to find a hallway under the stairs. There are Soopa Strikers in this hallway.
Go through the door at the end to find some Magiblots. There are three blocks at the end. Hit them to make a door appear. In the next room, you'll find three more blocks. Hit the middle one to make a door appear. In the room after that, there's a door and three blocks. Hit the right block to make the door move under the middle block. Go through the middle door to find some Red Chomps and a blue switch that removes the bars on the door. Go through the door on the right to find three more blocks. Hit them in the following order: middle, right, left. They are numbered in 3D. This makes a chestappear with a key. Go back to the stairs and climb up them. At the top are item blocks with a Happy Flower and Zombie Shroom and some Koopatrols. Unlock the door to the right.
The door leads to a small room that's actually a maze. Flip to see the arrows of which path to take to make the door to the right lead forward. You'll have to Super Jump to reach some platforms. The door leads to another hall of mirrors and Longadiles. Look for the window and jump through it to find a room swarming with Dimentios. They won't hurt you, but moving around will be difficult. Use Cudge to clear a path. There are chests and a Super Shroom hidden here. One has a Thunder Rage and another has a key. Go back through the window, then save before unlocking and opening the door.
Someone says they've made it here at last. It's Dimentio, mentioning that the heroes are missing the ravishing princess and the arm flailer. Tippi says they're not here to trade barbs with him and orders him to move out of the way. Dimentio says he will get out of their way and leaves, but later says he'll get out of their way once they defeat him. The heroes were worthy foes in the past, so he won't make it easy. They must come get him first, like it's a game of tag with magic. A space rift appears. Use Fleep's power on it to make a blue switch appear. Hit it to warp.
You warp to somewhere familiar: 1-1. Tippi wonders where they are and they notice Dimentio fly off. Keep an eye on the direction Dimentio goes and follow him. You don't need to finish the level, but to look for another space rift. Listen carefully for it, as it blends in to some areas. The space rift here leads to 2-3, Merlee's Mansion. The space rift is on the safe. Next is 3-2, the Tile Pool. The space rift is to the left of the item block with the Mushroom (Dimentio flies to the left). In 4-2, on Planet Blobule, the space rift is past the tall cliff. Flip to find a path past it. In 5-1, Downtown of Crag, flip and drop down to where you found the Fire Tablet. The space rift is to the left. In the destroyed Chapter 6, run with Dashell or Carrie and listen carefully for the space rift, as it blends into the background well. On the Underwhere Road, 7-2, climb up the area, without lit torches. The space rift is at the top, over a Dorguy.
This will take you back to Castle Bleck. Dimentio asks if they enjoyed the game of tag. Luigi tells him to stop messing around and fight them for real. Dimentio says he's not messing around. Magic is no laughing matter and he's always deadly serious. Dimentio's been watching them, saying they're the ones who can stand up to Count Bleck. He asks them a favor: will them help him destroy the count? Luigi asks why he's talking about betraying the count. Dimentio explains that Count Bleck betrayed him when he said he'd destroy all worlds and create new and perfect worlds in their place. Count Bleck was lying: he plans to obliterate all worlds and keeping them in ruin. Tippi is startled. Dimentio says he's always known about Count Bleck's nefarious goal, but he could never hope to stop the count on his own. Instead, he feigned loyalty to him and searched for someone to help him defeat the count. He explains that this is why he rescued the princess from certain brainwashing and sent them all to The Underwhere to fix the Pure Heart. He also a freed a man to be reunited with his brother. Tippi realizes that Dimentio's been helping them all this time. Diemntio asks them to return the favor and he'll give them the power to defeat Count Bleck if they fight side by side. Decline his offer. Dimentio says his offer drips with generosity and that with the Chaos Heart, they can rule every world. Reject the offer and Dimentio says he's wasted his time, so their game ends. He'll start with the green one, as the shag on his lip will make a fine trophy. Luigi is insulted, saying his moustache is not shag, but it's all Luigi. He tells Mario to leave Dimentio to him, as he doesn't have time to fight him when there are worlds to save. He tells Mario not to let Bowser's and Peach's sacrifices be for nothing, or his, either. Plus, it's personal: Dimentio made fun of his moustache, which he's sensitive about. Mario leaves. Dimentio calls the moment tender, saying he squeezed out a tear. He says Mario can run along and if he manages to defeat Count Bleck alone, all the better. He says he'll strike like an unseen dodgeball in an echoing gymnasium.
Dimentio has 80 HP and 4 attack. It only took a few hits with Luigi's attack doubled with his catch card. He'll create an illusion and shoot magic or try to trap Luigi in boxes. Hit the real one with a Super Jump and try to stomp him repeatedly. Once he's defeated, he cries uncle. Luigi asks if he's had enough. He didn't need his superstar brother to defeat him. Dimentio sees that Luigi's power is formidable, so he can't let Luigi fall into Count Bleck's velvet-lined gloves. He creates a box around the both of them. Luigi asks what he's doing and Dimentio says he has him now. They will both taste the agony of game-overing by magic. Luigi screams while Dimentio bids farewell as fireballs go off inside the box. Outside, Tippi calls to Luigi and the castle shakes. The door won't open. Tippi says they must grieve later, even though it's tough and it hurts. They must stop Count Bleck. The star is to the right.