Cartaphilus's Librarium

[This is a type of magic categorised as Runic Kithomancy]

One of the runic spells found in the Journal of Cartaphilus Agamemnon, this spell summons a spectral doorway that links to a persistent extra-dimensional library. This demiplane is infinitely large and can be used to store items as the demiplane persists outside of castings of the spell. The caster of this spell always knows the location of anything they wish to find, including the exit, however, those who enter the demiplane without the caster or wander off must succeed a DC17 Intelligence Saving Throw or become lost in the library, those who are lost in the library wander aimlessly, and if not found by the caster within 24 hours become a Shadow that is permanently bound to the demiplane.

The door of the demiplane can only be opened by the caster of the spell, and the door can only be interacted with or viewed by any creature that the caster chooses.

This spell ends after 8 hours, after which time, if the caster is still within the demiplane when the spell ends, they will be ejected into the nearest available space from the point where the door was summoned, any creature that is not lost in the demiplane that the caster chooses will also be ejected, otherwise, they will become trapped in the demiplane.