Universal constants, are they different from our universe? Gravity seems pretty close.
Gravity = 9.8 m/s^2
Speed of Light = 299,792,458 m/s
The Cleft - or at least the Middle Realm of the Cleft - is a sphere. It is not necessarily a solid sphere, like a normal planet, but it looks like one from the outside. The radius of the Cleft is approximately 1,600 miles. As the Immortals modify the Cleft, this figure is bound to gradually grow.
Planetary bodies outside the main surface of the Cleft (such as the moon, Zebes), retain the planetary properties they had in their original universes. Zebes is still a solid planet with a molten core.
Due to the Cleft being hollow, it is not as massive as a planet normally would be. Yet, it still has gravity equivilant to an Earth-sized planet. Carsanquay has a machine in the center of the Cleft that generates the missing gravity and compensates for other necessary physical forces.
The Cleft has three distinct realms:
Where did this place come from? I think MTS's origin story and the current story (shown with the 'story' command on the MUD) is correct except for that sword reference.
Stuff Falling In
Consequent to the Cleft only existing due to anomalous physics, the dimensional fabric of the Cleft is fragile. Frequently, rips open within the dimensional fabric. It is through these rips that pieces of other dimensions slip into the Cleft. This is generally a bad thing for the source dimensions, but this process is the source of all matter in the Cleft.
The Immortals are responsible for maintaining the integrity of the Cleft by figuring out to do with incoming pieces of other dimensions. Some are incorporated into the Middle Realm, others are shoved aside. Additionally, the Immortals - especially Carsanquay - are responsible for repairing dimensional rips before they grow too large.
It would be catastrophic if a black hole, supernova, or other high-energy cosmic phenomenon spilled through a dimensional tear.
It would be possible to escape the Cleft through a dimensional tear, but it would require a powerful spacecraft. Although people are able to enter the Cleft, it is believed that escaping would most likely kill any traveler due to the sudden change in fundamental physical laws uponing entering a new dimension. There is also the possibility of creating a temporal paradox dependent on the dimension to which the traveler escaped.