Realm Between Worlds

The Realm Between Worlds is a place where enthalpy rules in place of entropy. Instead of gravitational attraction, repulsion is the de-facto state of things.

Nothing in the Realm Between Worlds makes sense to a mortal mind. Even gods struggle to understand it. Time does not flow in a linear fashion. Rules are casually broken and reassembled on a whim.

It is a broken and nightmarish place, filled with strange architecture and stars in the sky that are living, tortured beings. Monsters dwell in this land-- called the Old Gods, or Old Ones, they are hideous and defy and semblance of natural order or evolution. Some are capable of inspiring insanity simply by being observed.

Younger, hungrier Old Ones periodically make their presence known at the edge of our reality. They peek into the rips and tears between the universe, reaching out to feed and snack. Sometimes they gain enough of a psychic foothold to project their will, allowing cults of devout worshippers to call them forth, or summon even greater, more malevolent entities.

Old Ones do not just threaten worlds, or life. They threaten reality itself, seeking to undo creation. Some, such as Trigon, are born of mortal malevolence and cruelty given life in the strange realm. Others, like Cthulu, can slip between the bonds of their reality and ours, though often slumbering and relatively quescient. Still others, such Azatoth and Yog-Sothoth, are so hideously alien and repugnant that they actively damage our universe simply by venturing near it. Should one of the Great Old Ones actively be summoned into reality, the response would be cataclysmic. The forces of Heaven and Hell and all temporal powers, even including primal abstracts like Eternity and Death, would take notice.