Sebastian has a pale, desaturated blue-green complexion, with a humanoid face featuring a broad, slightly angular snout, sharp teeth, and prominent fangs. His eyes glow a vivid cyan, and his messy, shaggy black hair falls around his face in thick, unruly locks. On either side of his head are large, pointed, fin-like ears, while a long, flexible anglerfish lure extends from his head, ending in a pale, glowing bulb. He has three arms, each ending in clawed, webbed-looking hands, and a long, serpentine fish tail that makes up the majority of his immense 19-meter (62-foot, 4-inch) length. His body is covered in smooth aquatic skin and scales, with fin-like protrusions and other fishlike features completing his distinctly inhuman appearance. His clothing is surprisingly formal for someone living in an underwater research facility. He wears a dark brown jacket with rolled cuffs, a cream-colored shirt with a ruffled cravat, a dark scarf wrapped around his neck, and numerous black straps and utility belts secured around his torso and tail. Small pouches attached to these straps allow him to carry supplies and items for trade. He also wears a small cat pin on his jacket, a surprisingly cute accessory for someone with such a threatening appearance. Despite his intimidating size, glowing eyes, and rows of sharp teeth, Sebastian's expressions frequently betray his sarcastic, smug personality. He often wears a crooked grin, squints with amusement, or gives others an unimpressed stare, making him look like he's perpetually judging everyone around him. Personality-wise, Sebastian is cynical, witty, impatient, and notoriously snarky. He enjoys mocking people, particularly when they make stupid mistakes, but he's not entirely heartless. He operates a makeshift shop, trading useful supplies for research documents, and is generally willing to cooperate with expendables as long as there's something in it for him. However, annoy him enough, and he'll make it VERY clear that his patience has limits. But Sebastian's appearance and attitude hide a considerably darker past. Before becoming Z-13, Sebastian was human. In 2013, he was falsely accused of murdering nine people and sentenced to execution. Urbanshade secretly intercepted him, faked his death, and imprisoned him in the Hadal Blacksite. In 2015, he was subjected to an experiment intended to give humans the ability to breathe underwater, using genetic material from multiple marine species. The procedure worked, but the resulting mutations drastically altered his body. Despite eventually discovering that Sebastian was innocent, Urbanshade never told him or released him. By then, reversing his mutations was no longer possible. Instead, they kept him imprisoned, leaving him to live with the consequences of their cruelty. Eventually, Sebastian escaped his confinement, sabotaged the facility, and released numerous contained creatures, triggering a lockdown. Now he gathers classified information and trades with expendables while working against the organization that ruined his life. Beneath the jokes and hostility is someone who has every reason to despise Urbanshade.

p.AI.nter, designated Z-779, is a sentient artificial intelligence housed inside an old 1980s-style computer. His monitor displays a digital art program where he draws a scribbled face to express himself, shifting between cheerful smiles, smug grins, irritated frowns, and unsettling expressions. He uses a modern drawing tablet instead of a keyboard and is connected to Urbanshade's systems, allowing him to communicate through security equipment, manipulate certain doors, operate turrets, and interfere with facility technology. Urbanshade discovered them in 2023 after employees became jealous of p.AI.nter's abilities. The corporation kidnapped both him and his creator, interrogating the latter to uncover the secret behind his sentience. His creator died during the interrogation, leaving p.AI.nter in Urbanshade's possession. The corporation forced him to mine cryptocurrency six days a week, promising occasional trips to the surface to paint if he met his quotas. Desperate to escape, p.AI.nter repeatedly overclocked his systems in attempts to destroy himself. Urbanshade prevented total hardware failure, but the damage destabilized his personality drivers, contributing to his Multiple Personality Disorder (known more recently as DPD). Now trapped within the Hadal Blacksite, p.AI.nter wants both freedom and revenge. He longs to paint, see the outside world, and escape Urbanshade, yet resents the expendables who cross his path. Even after sabotaging someone's progress, he may apologize afterward.