Dark Secret

Truth can be even more deadly than a knife to the heart.
You whisper a phrase into the mind of the target, unknown to you but clear and terrifying to them. Until the end of your next turn, you have advantage on all ability checks, attack rolls, and saving throws involving your target or actions it has taken. During this time, the target has disadvantage on all ability checks and attack rolls involving you or actions you have taken. Targets that are immune to being frightened are immune to this effect.

At Higher Levels: When you cast this spell using a spell slot of 3rd level or higher, you can choose one additional target per spell slot level above 2nd.