Demiplane

Target. A flat, solid surface that you can see within range.

Effect. You create a shadowy door that is large enough to allow Medium creatures to pass through unhindered. When opened, the door leads to a demiplane that appears to be an empty room 30 feet in each dimension, made of wood or stone. Each time you cast this spell, you can create a new demiplane, or have the shadowy door connect to a demiplane you created with a previous casting of this spell. If you know the nature and contents of a demiplane created by a casting of this spell by another creature, you can have the shadowy door connect to its demiplane instead.

Special. When the spell ends, the door disappears, and any creatures or objects inside the demiplane remain trapped there, as the door also disappears from the other side. If you cast this spell while on a demiplane, you may instead connect it to the last non-demiplane location you were in.

At Higher Levels. The size of your demiplane doubles for each slot level above 8th. At the DMs discretion, you may be allowed to alter the demiplane, such as by dividing it into separate rooms, altering gravity, shape, or season, or giving it an ecology.