5e SRD >Feats >

Mage Slayer

You have practiced techniques that are useful in melee combat against spellcasters. You gain the following benefits against creatures with a spellcasting feature that is not innate: Your melee attacks do an additional 1d6 damage against creatures with the spellcasting feature that is not innate.

When a creature within 5 feet of you casts a spell, you can use your reaction to make a melee weapon attack against that creature. When you damage a creature that is concentrating on a spell, that creature has disadvantage on the saving throw it makes to maintain concentration.

Section 15: Copyright Notice

Cloak & Coin Campaign Setting Copyright 2021. Red Turban Press, Inc. Authors: Laljit Sidhu, Bjorn Dingeldein, Jon Giordano