Real name: Error404 Sans. The sole survivor of a collapsed world, he is the mastermind (anti-hero/villain) who controls and operates within the Multiverse from the shadows. Known as the God of the Multiverse. He made a contract with Error!Sans, promising to help him erase all remaining AUs once Alphatale is complete, taking him as an apprentice and using him from behind the scenes. He wears a long blue coat with blue sashes marked with the number 4 on both arms. He wears a white shirt, white pants, black socks, and white slippers. The white fur on his coat and sleeves, as well as his slippers, are marked with random blue straight lines. Black lines resembling a spiderweb droop from beneath his eyes (actually scars). His right eye is a blue hollow circle. His left eye is a blue hollow circle with a white center. His teeth are bright blue. The base of his fingers is black, and the tips are blue. The rest of his body consists of white bone.

The Destroyer of AUs. The future form of Geno!Sans, who ignored the warnings of Undertale's Sans and continued to use the power of Determination. He accidentally sent himself to the Anti-Void and transformed into Error. He currently resides in the Anti-Void. He is the apprentice of Error404. He appears as a skeleton covered in glitches with almost entirely black bones. Both eyes have red conjunctiva. The pupil of his right eye is small and white. The left eye is layered with yellow, blue, and black from the outside in. Because his eyes were often covered in glitches when he was Geno, his eyesight is poor (especially in the right eye). His fingers are red and yellow, turning black at the base. His feet are red. The inside of his clothes, visible from the hem, is yellow.

In reality, King Multiverse was originally PhotoNegative!Sans. He was kidnapped by Error404!Sans and created by being submerged in the Mainframe pool. Occasionally, he reverts to his original state; depictions in the Alphatale story show King Multiverse returning to PhotoNegative!Sans. Error404 has erased all of his memories from when he was PhotoNegative. When he was created in the Mainframe, Error404 tore off a piece of his own finger and threw it in, so King Multiverse's code contains a portion of Error404's code. He is treated like a king. He stands 204cm tall with a monarch-like appearance and always maintains perfect posture. He wears a black jacket that appears purple due to the light emitting from his eyes. He wears a brown scarf for fashion. The hem of his jacket has a deep sky-blue zipper. He wears a sky-blue breastplate over his shirt, which can absorb kinetic energy to withstand direct attacks. The right half of his body is black with thin neon purple marrow inside. The left half is simple white. He wears the same shorts as Undertale's Sans as a nod to his origins, along with gray slippers.