Glibness

Bard    Warlock

Level 8 Transmutation

Casting Time: 1 action
Range: Self
Components: V
Duration: 1 hour

Until the spell ends, when you make a Charisma check, you can replace the number you roll with a 15. Additionally, no matter what you say, magic that would determine if you are telling the truth indicates that you are being truthful.

Source: Player's Handbook, p. 245