Spell Defender

General Feat (Prerequisite: Level 4+)

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

You can take a Reaction to cast a spell at the creature rather than making an Opportunity Attack. The spell must have a casting time of one action and must target only that creature. You also trigger opportunity attack whenever a creature makes a melee attack at you or an ally within 5ft.