The kingdom's former Court, a short, pudgy, imp-like jester featuring a round gray face, elven ears, clown-like eyes with small yellow pupils and black sclerae, long purple tongue, and large smiling mouth with yellow, sharp teeth. Wears a purple and black harlequin hat, shirt, black trousers, a dark cape, lime green and yellow collar, and a purple J-shaped tail. A lunatic who believes to have "freedom" despite being imprisoned, he invites others to be "free" alongside him. He fell into madness after meeting a "strange someone", and now sees the whole world as a game. He possesses chaotic reality-warping abilities; shapeshifting into a giant scythe via Metamorphosis, teleportation, stretch his body parts, projectile danmaku attacks, and claims he can "do anything".

A enygmatic entity, the one who created the Card Kingdom's Dark Fountain that Ralsei wants sealed, with King having sworn his loyalty to the Knight. Has an amorphous, shadowy, and shifting physical appearance featuring long limbs, pointed legs, jagged shoulder protrusions, and a helmet with a single circular aperture that morphs into a face or mouth. Possesses powers such as fountain creation, dark magic, spatial manipulation, summoning crystal barrages, executing precision horizontal, vertical, and diagonal sword dances, and altering gravity and the game board during combat. A cunning and sinister mastermind and a sly trickster, feigning weakness to trick others into lowering their guards. The Knight seems to be a shrewd and sinister manipulator, tricking Darkners into furthering its schemes to create more Dark Fountains and presumably the Roaring. His unnatural visage and enigmatic aura make it a menacing opponent, he seems to be very aware of this, striking poses to taunt and intimidate whenever possible, displaying its arrogance and making them aware of its incredible power.

A cynical shopkeeper. Formerly the court magician, he looks like a tall anthrophomorfic musculad stuffed toy cat with a blueish-purple face, brown clothing, and mismatched, stitched facial feature, with a orange scarf around his neck. His left eye socket is empty and almost closed and the right one entirely replaced with a button, sometimes the holes on it rotate. From beneath it runs a scar. He possesses a cynical, nihilistic, and weary personality masked behind a polite, welcoming demeanor, displaying a sense of apathy toward ongoing chaos, believing that a darker fate will arrive eventually regardless of what anyone does. Retaining a deep, mysterious understanding of shadow crystals, secret bosses, and the grim realities of the Dark World.

Gaster's Executor. He blends in so well with the others that even his name in the files is the most normal thing ever. A tall muscular gray bird monster that has a large head, large eyes and beak, a long neck, short wings, and stubby feet. They appear to angle their head downwards, as if leaning over. Acting to keep anyone from discovering it, with many thinly-veiled warnings to stop investigating. Displays a pensive, superstitious, uneasy personality, characterized by a mix of nostalgic admiration for Dr. Gaster and sudden, fearful paranoia.

Cat-like creatures with friendly faces and a penchant towards laughter that show up in the strangest places, having a wide, crooked "slasher" smile with mismatched pink and yellow eyes. The reason for their presence is unknown, but various clues imply they have a more relevant role in the story than it seems. They aren't too smart and rather are a violent hunting party sent by a certain "someone" to chase targets down. Appear in dark voids, everything blending seemlessly into the background but the mouth and eye, being predators feared for their persistent protein-hunting abilities.

A smith, historian, author and teacher beloved across the entire world for his Lord of the Hammer book series. Being an elderly, large, olive-green tortoise monster with a dark brown shell, crooked yellow teeth, pink eyebrows and beard, One yellow eye is visible while the other is completely closed. Dons gray-silver armor, gloves, and sabatons, wields an incredibly large war hammer and moves quickly. Confident, charismatic, and mischievous, blending a wise scholarly demeanor with a playful, testy attitude. Deeply understands history and lore, although he can be a bit scatterbrained when recalling minor details. Acts as a natural and inspiring mentor, although he enjoys testing others with a bit of dry humor and tough love. Rejects blind obedience to fate, encouraging others to break free from rigid paths and write their own futures. He wields and can conjure hammers of varying sizes out of thin air, displays immense speed, agility, and reflexes, and can deflect magic attacks back at opponents using his hammer.