Keystone Staff

Dressed limestone bound in iron, short and heavy, wedge-cut at the top like the block at the crown of an arch.

Only wizards and clerics may unlock its magic. Each charge seals one room for ten minutes so that nothing may enter or leave it by teleport, gate, summoning, or passing through walls. When depleted the staff still holds up any arch or doorway it is propped in, whatever weight sits above it.