A little while after accepting Bowser's challenge, Sora and the Mario brothers start their adventure just outside of the castle grounds only to be encountered by Shadows, Goombas, and Koopa Troopas on the first trail. The three heroes made it to a warp pipe that leads underground only to be jumped by the same enemies, but this time with some help. Creeper Plant Heartless and Pirahna Plants. While the Pirahana Plants were chomping, the Creeper Plants were either shooting out seeds or sticking out their roots. Sora yanks the roots pulling out the plant-like Heartless only to expose it's whole self. Mario and Luigi uses their Fire abilities to whack those weeds as Sora uses Fire Raid on them. They made it above ground again, only to have Koopa Para Troopas along with Air Soldiers, Aeroplanes, Air Pirates, and Silver Rocks coming at them. The trio manage to swat any enemy that came their way until the eventually reach the first castle. It was a big red castle, but it the emblem of the Heartless on the front. They entered the castle to find it to have boiling lava. The lava had fireballs jump out with flame rods spinning around. But it was crawling with Shadows and Soldiers as well. The three of them made it to the enterance of of the final room.

Sora: Looks like the place.

Mario nods in agreement, as our heroes enters the room. They ready themselves for the fight.

Sora: Game's up, Bowser!

Kamek: Hee, hee, hee!

Sora, Mario, and Luigi all have confused looks on their faces. As the gates opens, a Goomba walks into the room.

Sora: What is this?

Luigi: Peach isn't in here after all.

Kamek: You're darn tootin', Uigi.

They look around to find the voice but they couldn't see who was speaking.

Kamek comes flying in on his broomstick.

Luigi: Kamek?!

Kamek: Did you really think that we'd make it easy for you right at the start? You pudding heads are no smarter than this Goomba in front of you.

Sora: What's that suppose to mean?

Kamek: You'll see right now. Listen, little Gooma! Why don't you just stomp on these little invaders. Kamek flies across the room as he sprinkles his magic everywhere. The Goomba gives off a cascading glow of pink and yellow. The glow fades as the Goomba grows into the size of a Behemoth Heartless. The newly grown Mega Goomba starts off marching towards the brave trio (brave duo excluding Luigi) as Mario starts throwing fireballs at the Mega Goomba, while Sora uses his Ars Arcanum on it. Luigi hits it foot with a hammer which only aggitated the Mega Goomba. Mega Goomba jumps up and down summoning Mega Shadows for assistance. Sora uses his summon command to call upon Genie for help.

Genie: Genie of the Lamp at your service!

Sora: Genie! Get rid of those Heartless!

Genie: One Heartless disappearing act, coming right up!

Genie snaps his fingers as a sparkle from the Mega Shadows disappears. Luigi was amazed at what he saw.

Luigi: Wow...

Sora: I know, right?

Genie: Show this overgrown fungus whose boss around here!

Mega Goomba: (Roar) Overgrown fungus?! I'll show you to dis' me you blue pitstain!

Mega Goomba jumps towards Sora as he uses his Strike Raid on it. It paralyzed the Goomba monster giving Sora a chance he needed to jump on his head. The Mega Goomba gives off another angry look.

Mega Goomba: You damn brat! I'll stomp you into dust for that!

Mega Goomba jumps towards Sora as Mario jumps on top of his head; Sora uses Time Slicer on Mega Goomba as he takes a series of hits from the Keyblader. With the final blow given the gigantic Goomba shrinks but so much smaller than before. The Goomba gave off a scared look on his face as he's just in stomping range of Sora's shoe. Sora is about to step on him, but the tiny Goomba ran as fast as his little feet can carry him. With the battle done, our heroes knew that there only six more castles to go.

Meanwhile, at Bowser's castle.

Bowser: So you failed to stop them?!

Kamek: Forgive me, Lord Bowser. That Goomba was just so incompetent. But rest assured, I have other surprises for the Mario brothers and the boy.

Bowser: Well, you better not screw up again, Kamek, or you'll pay the same price as the Goomba, but even more so.

That was chapter 3, but chapter 4 will be up soon enough.