Loki's gift makes even the most barefaced lie seem strangely plausible: you gain advantage to Charisma (Deception) checks for whatever you're currently saying. If your Deception check fails, the creature knows that you tried to manipulate it with magic. If you lie to a creature that has a friendly attitude toward you and it fails a Charisma saving throw, you can also coax him or her to reveal a potentially embarrassing secret. The secret can involve wrongdoing (adultery, cheating at tafl, a secret fear, etc.) but not something life-threatening or dishonorable enough to earn the subject repute as a nithling. The verbal component of this spell is the lie you are telling.