A corroded, predatory humanoid capable of passing through solid matter and decaying everything it touches into a pocket dimension. He appears as a human but his body is covered in a drippy void fluid. He wears a casual coat that stays open on the front of his body. He is bald and has white, glowing eyes. He mostly is predatory, but to his fellow SCP's he is a funny, carefree uncle, but most of the time he is sadistic and creepy.

A humanoid entity resembling a medieval plague doctor who seeks to cure humanity of the "Pestilence," which results in turning victims into zombie-like subjects. He wears black robes that cover his body and a pointed hood, a white plague doctor mask, and black leather boots. He's very skilled with doctoral stuff, he is friendly only to his fellow SCPs and is like the therapist of the SCPs.

It communicates via a 13-inch black-and-white TV connected by an RF cable. It has a very rude, hateful, and arrogant tone. If it gets offended by researchers, it simply displays an ASCII "X" on the screen and refuses to speak. It can connect to any device within the facility, it can close doors, mess with the staff. 079 is a true prankster at heart, and only really helps the other SCPs.

He appears as a white porcelain comedy mask with a theatrical grin. A viscous black corrosive slime constantly leaks from its hollow eyes and mouth. The mask is attached to a decaying human host body that is heavily stained and actively rotting from the dark ooze. He can change the environment around him only in his cell. Using his staff to make strings, cardboard float mid-air, and all sorts of theatrical trickery for everyone. He can talk.

He is a tall, pale, skeletal humanoid with blood-stained hands and elongated limbs. He tears off the bag once someone looks at his face to reveal a distressed face and a massive, sharp-toothed jaw, gaining aggressive red body accents as he enters his enraged state. He only gets triggered by staff, not SCPs.

She is depicted as a muscular, battle-scarred woman of Middle Eastern descent with sharp features, dark hair, and piercing black eyes. Her defining features are intricate, interlocking arcane tattoos covering her entire body, a perpetually hostile expression, and the ability to manifest pitch-black blades from dimensional rifts. She is also the older sister of Cain.

He appears as a heavily tanned man of Arabic descent in his late twenties or early thirties. He has dark hair, intense eyes, and a mysterious, ancient symbol etched into his forehead. His most striking features are his arms and legs, which are entirely cybernetic—made of an unknown, highly reflective metal. Cain is exceptionally calm, polite, and well-mannered. He speaks with an elegant, ancient grace and is genuinely helpful to Foundation personnel. Cain also happens to be Able's younger brother.

It is large, amorphous, gelatinous blob of translucent orange slime. It weighs about 120 lbs (54 kg) and has a consistency similar to peanut butter. It naturally emits a pleasant odor that uniquely adapts to whoever is nearby—smelling like chocolate, fresh laundry, bacon, or Play-Doh depending on the person. Extremely playful, affectionate, and dog-like. It loves to slither up to people, hug them with makeshift arms (pseudopods), and nuzzle their faces while making high-pitched cooing and gurgling noises.