(Since literal angels and ghosts exist in Pressure, let's just assume that there are magical things that can turn monsters into humans for story purposes)

Deep Solace was born as a humanoid fish mutant that would be the closest biological thing to a merperson. Technically, he was natural, but only because his father birthed him and he wasn't the cause of direct mutation unlike Sebastian. And as cool as it was to have three arms and be able to swim around easily, he wondered what it'd be like to be a human boy. He thought humans were interesting as much as Sebastian said they were heartless and would only hurt their kind. It was the main reason why Deep wasn't allowed outside of the shop Sebastian ran in the facility. But one day, as Deep was going out for a supply run, he found a divot in the ground filled with water. But it looked funny, taking on an odd purplish color. Being as curious as he was, he decided he'd take a small swim. He wouldn't drink it obviously, but being super absolutely AMAZINGLY smart, he decided swimming was 100% safer. And so, he discarded his makeshift clothes and dove in, feeling a slight tingling under his scales as he swished around. Soon enough, he rested himself on the edge of the pit, sighing as he relaxed. He stretched out, his two arms above his head and using his third to-Wait, where was his third arm? Quickly, he looked at himself, and a soft gasp left him as he saw he had only two arms. And they had skin. Human skin...! He was a human boy! With normal eyes! And normal flesh! And legs!