Being a Mage Slayer feat in dungeons and dragons you practiced some techniques which are helpful in melee combat against to the spellcasters, this feat can give below mentioned advantages:
- Whenever the creature within a reasonable reach you are able to take the opportunity attacks casts a spell, you can also use your reaction for making a melee weapon attack that against to selected creature.
- Whenever you would damage the creature which is concentrating on the spell, they already have a disadvantage on a saving throw that it makes to maintain concentration.
- You also have the advantage on a saving which is against spell cast by creatures with your reach in time.