Plainspeak Cup

Dark horn, shallow, with a silver rim and a hairline crack down one side that has never leaked.

A full measure of water drunk from this cup holds a creature to plain speech for ten minutes: it cannot speak, write, sign, or gesture anything it believes to be false. It may refuse to answer, stay silent, or walk away, but it cannot answer falsely, and no charm, compulsion, oath, or magic short of a god's own overrides this. A creature made to drink against its will resists with a Mind save, and one that saves cannot be held by the cup again until the next dawn. Works on any creature that can drink. Water standing in the cup clouds within a minute if there is poison in the room.