Create Demiplane

 You create a finite space on the fringe of an existing plane of existence. The nature of the space is initially chaotic and random, but the caster can mold the space in small or large ways by making Intelligence (Arcana) checks of an appropriate DC (set by the DM). Each check costs one additional hour of the casting time. Failing a check causes the caster 1d6 psychic damage, or 3d6 psychic damage if the caster fails by 5 or more. The initial space is spherical, of a diameter equal to the caster's INT score x 100 ft.  The border initially manifests as a silvery mist but can be altered by the caster just like any other property of the demiplane.

Once the spell completes, the demiplane is tied to the caster and the caster can use Plane Shift or similar magics to reach the plane.  The caster will also be aware of the anchor point of the demiplane, though they do not automatically have access to it. Touching the anchor point immediately transports a creature to the demiplane. Any other creature trying to reach the plane must have some tangible physical essence of the plane, be it dirt, water, stone or any object completely from the created space. Alternately, a piece of the caster's flesh may be substituted. Without this component the plane cannot be reached, contacted, or in any way found through Divination, although Wish or Divine Intervention have a 5% chance of revealing the anchor point.

An initially created demiplane is extremely fragile and prone to shrinking and being erased from existence. Repeated castings of the spell can cause the area to double in size and stabilize the space. Some demiplanes have been seen with hundreds of miles of area or more.

The demiplane is sensitive to the state of the caster and can thrive or wither as does the caster's form. While present in the demiplane, the caster can manifest the following magical effects as the respective spell:

• Create Food and Water
• Control Weather
• Heroes Feast
• Creation
• Magnificent Mansion

These effects cost the caster a spell slot of the appropriate level. The caster does not need to memorize or even know the spell. There is a 5% chance that manifesting the spell causes the caster to spontaneously learn the actual spell, allowing them to transcribe it in their spellbook. If the caster does not have a spell slot of the appropriate level, the spell still works but the caster takes 1d6 psychic damage per level of the spell used.

In some cases the control of the demiplane can be wrested from the caster by another powerful entity, but this can only be done when the caster is first severely weakened. 

Initial State: