- "Enemy, enemy, be now quiet [...] Let your deceitful tongue ... be broken. Let no untruths ... be spoken."
- ―Rupert Giles[src]
The truth spell was a spell that witches and other magic practitioners used to force enemies or otherwise to tell the truth no matter what. This spell called for motherwort and the incantation above.
Rupert Giles attempted to use this spell on Spike in order to force him to tell the Scooby Gang where The Initiative lab was. However, he was not able to complete the spell because he had gone blind due to Willow Rosenberg's "My Will Be Done" Spell.