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“Lies… they’re painful.”

When a being lies around a Kyanite, the Kyanite will here a particularly high pitched noise that alerts them to the potential lie. The more loudly and persistently a lie is spoken, the more painful it can end up being for the Kyanite.

No one else can hear the noise a Kyanite hears, but I imagine it being similar to this: https://youtu.be/FqDmIRRseWg