This spell renders the target's flesh and blood (but not their internal organs or bones) transparent.
For the duration of the spell, the target will be unable to lie.
The name of their true love will also be written, in letters of gold so tiny that no eye could see them, on their heart. Some say that the word 'good' or 'evil' will appear on those of appropriate character.
It is said that the witch Zohar Longshanks discovered a new version of this spell, stronger than the old as stock is to soup. The effect was permanent, so much so that a parent would pass it on to their child. She is said to have cast it on herself and a few followers, and started a community on an isolated island. Stories disagree as to whether the island is a paradise of perfect truth and honesty, or a nightmare where not even thoughts are private.