Passwall

A passwall spell enables the spellcaster to open a passage through wooden, plaster, or stone walls, but not other materials. The spellcaster and any associates can simply walk through. The spell causes a 5-foot-wide by 8-foot-high by 10-foot deep opening. Several of these spells can form a continuous passage so that very thick walls can be pierced. If dispelled, the passwall closes away from the dispelling caster, ejecting those in the passage.

Note: This version of passwall originally appeared in the 2nd Edition Player's Handbook for Advanced Dungeons & Dragons from TSR. Its use here is for the purposes of providing context for the campaign only.