Palcheok-gwisin is the mutated form of Japan’s Hasshaku-sama after it crossed into the Korean internet. It is described as roughly eight cheok tall (about 2.4 meters) with distorted joints, and those it fixates on are said to die within days.
It is fundamentally a case of meme horror — a creature that transmits and transforms through media. Each retelling adds and alters details, so it grows with the line between original and copy left blurred.