Warcaster, Variant (5e Feat)
From D&D Wiki
Prerequisites: The ability to cast at least one spell, Two-Weapon fighting style
You have practiced casting spells in the midst of combat, learning techniques that grant you the following benefits:
-When you make an attack as part of casting a cantrip with a light weapon and are wielding a light weapon in your offhand, you may take a Bonus action to gain advantage on the attack roll.
-You can perform the somatic components of spells even when you have weapons or a shield in one or both hands.
-When a hostile creature's movement provokes an opportunity attack from you, you can use your reaction to cast a cantrip at the creature, rather than making an opportunity attack. The spell must have a casting time of 1 action and must target only that creature.