Petty

Increase your Intelligence, Wisdom, or Charisma score by 1, to a maximum of 20.

You learn the cantrip Vicious Mockery. Your spellcasting ability for this is the score you increased with this feat.

Reactive Mockery. When a creature that you can see within 60ft. of you fails an attack roll or saving throw, you can use your reaction to cast Vicious Mockery targeting that creature.