Passwall

Passwall creates a passage through wooden, plaster, or stone walls, but not through metal or other harder materials. The passage is up to 10 feet deep plus an additional 10 feet deep per three caster levels above 9^th (20 feet at 12^th, 30 feet deep at 15^th, 40 feet deep at 18^th). If the wall's thickness is more than the depth of the passage created, then a single passwall simply makes a niche or short tunnel. Several passwall spells can then form a continuing passage to breach very thick walls. When passwall ends (due to duration, dispel magic, or caster's choice), creatures within the passage are ejected out the nearest exit.