Periapt of Proof Against Lies

Wondrous itemrare

A pendant fashioned from the claw or horn of a Pact Drake (see Creature Codex) is affixed to a thin gold chain. While you wear it, you know if you hear a lie, but this doesn't apply to evasive statements that remain within the boundaries of the truth. If you lie while wearing this pendant, you become poisoned for 10 minutes.

Source: Vault of Magic · OGL-1.0a · 5.1