Night stone

From Sword of Truth Wiki

A night stone was a stone that would give off a brilliant white light when taken out in night, but only if used by the owner. The stone must have been given to its current owner as a gift with no strings attached. When used however, a night stone would also call spirits of the dead to it, putting the user in great peril.

Adie the bone woman gave one of these to Richard Cypher and Kahlan Amnell before crossing the Boundary through means of a small path. Without knowing he would call spirits from the Underworld, Richard used the night stone and barely escaped between them and the narrow confines of the boundary's passage.