Buffoon's Sword

This blade seems and behaves in all ways as a sword of subtlety until actually used in combat. Once used in combat, it imposes a –10 penalty on all Stealth checks made by its wielder. It also makes it nearly impossible for the owner to tell a lie or engage in any other sort of subterfuge. Each time he does so, he must make a DC 15 Will saving throw to avoid blurting out the truth or taking some other involuntary action that spoils his attempted ruse. Only curse-ending magic can rid the wielder of the sword once its curse activates.

Magic Items sword of subtlety