Limbo's physical laws are primarily magical, though laws of the ordinary universe (such as electromagnetism and gravity) normally apply within its bounds. It has an ecology composed primarily of demons of various sizes, strengths, and intellects. It is said that its ether is much thinner than that of the normal universe, allowing for a greater spectrum of magical powers and effects. All demons within it are magical creatures that possess spell making abilities to a greater or lesser degree. Although Otherplace has a linear history, time within it is not rigid. Many points in its past and future are connected through naturally occurring temporal rifts, and its present is relative to the individual. Its history can be changed by travel through these rifts, but for some reason this is rare. Limbo is traditionally ruled by a Supreme Sorcerer, either a demonic native or an entity from another universe, often Earth's. Limbo's appearance and physical laws are highly variable, and determined by the power and personal taste of its ruler. The reality of Limbo is generated by a single deposit of a magical metal called promethium. In Limbo it takes the form of a giant animal heart, hidden in a cavern deep below its surface. Removal of the promethium to another dimension will cause Limbo to vanish.