Although lacking a physical body, Spiritomb projects its appearance out of a small rock called the Odd Keystone. The rock is trapezoidal in shape and has two small dots. There is a crack running down the middle, splitting in two near the bottom. The crack in combination with the two dots appears to form a frowning face. Spiritomb's projected appearance is an ethereal composition of swirling purple fog. Its face is set in the middle of the fog and contains green, crescent eyes that are connected to its jagged mouth. Its pupils are composed of a spiral and it is sometimes only seen with one. Swirling around its face are green orbs with yellow centers.
Spiritomb is formed by the collection of 108 spirits being trapped in an Odd Keystone due to misdeeds. Some Spiritomb are up to 500 years old. As seen in the anime, Spiritomb can be just as aggressive and destructive as the spirits that it is composed of. It will lash out at anyone with little thought, often exercising short sightedness in its pursuit of vengeance.