So, here it is. Man, this took me way longer than it should have, but I got it done. For new readers, understand that I began writing this before season four even started, so a few things might be off-canon. I hope you can enjoy it despite a few continuity errors. I don't own Adventure Time.
All was peaceful in the candy kingdom; the denizens bustling through the sugar coated streets, on their way to perform their daily activities. Atop her tower, Princess Bubblegum sat in a meditative position on her yoga mat, looking down at her kingdom. Yes, it truly was a paradise.
Unfortunately for her, the tranquil state of the kingdom would not last much longer, as in the streets, a mysterious cloaked figure dropped something as it passed by the castle entrance. No one noticed him drop it, nor did they see whatever he had dropped scurry into the castle. The figure applauded the subtlety in his task, as well as that in his rodent-like companion's, but decided that stealth and subtlety wouldn't be enough for the mission at hand.
In an instant, his cloak flew from his form, revealing a young man, seemingly in his late adolescent years, with long hair colored red, yet tinted so dark one would at first consider it black, with the points of long ears peeking out from the sides. He wore a white shirt under a black overcoat, the cuffs of the shirt rolled over the ends of the coat sleeves. He wore dark black slacks that were slightly too long and bunched up at his ankle and heeled shoes made of brown leather that pointed at the toe. On his head he wore a wizard's stocking cap, part of the brim folded and pinned to the crown of the hat with a button that was black with a white question mark on it. From his coat he drew a long wooden staff, slightly longer than he was tall, and much too long to be able to fit inside his jacket, that ended in a green orb; the wood seeming to have grown around the orb, swirling into question mark shapes around it. On the bridge of his nose rest a small pair of black sunglasses, that obscured the bottom half of his eyes.
"Candy Kingdom, hear me!" he bellowed, gathering the attention of the candy people. He flew into the air as if being dragged by his staff and continued speaking. "Watch this!" he shouted, as many fireworks erupted from his staff in a beautiful display of lights.
Though the candy people found the display amusing, princess bubblegum clearly saw through the magician's ruse. "Candy Golems! Remove him!" she commanded. On que, the bubblegum towers turned and reached out to grab the wizard. Predicting this, he flew out of their grip and blasted their hands with blue energy, freezing them together. The golems fought to get their hands free from one another, and while watching the amusing display, shot another ray of energy at the ice, causing the golems to fall backward from their own weight, helpless to get back up.
Basking in hubris, the wizard floated himself up to the princess as she sat perched on her balcony. "Come now, Bonnibell, you should know that won't work on me." he said.
Princess Bubblegum smirked "I'm aware of this, and you'll be less than happy to know that in light of recent events, I've made a few improvements to the royal guards of the candy kingdom."
"You think your brigade of candy-clad marshmallows can do anything to me?"
"Like I said, I've made improvements to the new guards." Princess Bubblegum pressed a button on her wall. In an instant, panels on the castle opened, and out flew taffy-men with molded wings and sharpened candy-canes. The magician released a torrent of fire, but flew off as he found that whatever Bonnibell had done to them made them fireproof. He heard her yelling from her balcony. "You're not going to like these guards! They're sugar-free!"
Clever Girl he thought as he flew to the ground. Though flying to ground level proved to be not the best idea, as large rock candy golems littered the surface. One knocked his staff from his hand, while another picked him up, binding his arms.
"I'm sure you would like to think you've got me." he said. The lack of reply from the golems confirmed his assumption that the beings were non-sentient. With a flick of the wrist, his staff returned to his hand, where it was used to blast each of the poly-colored golems with magic energy. Flying into the air, the magician looked down upon the candy kingdom, and taking notice of all of the new guards, it suddenly became clear to him just how long he would have to be there.