Phase Door

When this spell is cast, the magic-user attunes his or her body, and a section of wall is affected as if by a passwall spell (q.v.). 

The phase door is invisible to all creatures save the spell caster, and only he or she can use the space or passage the spell creates, disappearing when the phase door is entered, and appearing when it is exited. 

The phase door lasts for 1 usage for every 2 levels of experience of the spell caster. It can be dispelled only by a casting of dispel magic from a higher level magic-user, or by several lower level magic-users, casting in concert, whose combined levels of experience are more than double that of the magic-user who cast the spell.

This spell provides an escape route for high level magic-users, although phase spiders can see and use it with ease. A gem of seeing, true seeing, and true sight will reveal the presence of a phase door.