Unerring Delivery

You obtain two kind letters one is Diplomat’s Letter and the other is Letter of Termination.

When combat starts you may gift a Diplomat’s Letter to a number of creatures equal to your proficiency bonus.

Each creature may choose to accept the letter. If they accept your letter they Receive the Diplomat’s Letter.
Diplomat’s Letter. When you gift this letter the creature is unable to take any action to harm or cause you to have a detrimental condition until the end of combat or until you deal damage to them.
If they refuse the letter you may now attempt to deliver a Letter of Termination against that creature later in combat (see below).
Letter of Termination. You may attempt to gift them this letter as a bonus action. Choose AC, Saves, or Attack Rolls. They may accept the letter. If they do they have penalty equal to your wisdom modifier to the choice until the end of combat. If they refuse they take 10d6 psychic damage times the number of attempts you have made against them this combat.

Once a creature has accepted a letter you cannot attempt to deliver a letter to them until the next combat.