Truthsayers are trained by the priesthood of the Haighlei Empire to touch a person's soul and use what they sense to discern truth from falsehood with 100% accuracy. This soul-touching, or heart-reading, is an intimate act on the part of the Truthsayer, though the person being tested feels nothing.
The Truthsayer takes in the essence of the other person, well beyond the level of any thoughts or surface emotions. They then relate this to the possible truth of what the person is saying. This type of mental touch goes much deeper than anything a Mindspeaker or Empath might sense, and there are drawbacks for the Truthsayer. While Reading a pure, noble soul can bring the Truthsayer pleasure and energy, Reading a vile, corrupt soul can leave them drained and ill.