Mage Slayer feat in DnD 5E explained

The Rogue panted as she eyed Lich before with caution, studying the decaying physique that lay beneath its warded robes, alert for the slightest twitch that would betray its next move. In the background, she could hear the battle cries and gasps of pain of her allies, locked into combat with the Lich’s summoned horrors. The ancient evil raised a bony finger, sending a thing beam of green energy towards the Rogue, prepared she nimbly dodged the side and struck out with the glowing scimitar she held tightly. The blade caught the Lich unprepared at the end of its casting, the blade cutting deep into its desiccated flesh and shattering its concentration. As the summoned creatures faded out of existence, and her allies began to dash towards the source of the problem, she smiled and brought her scimitar up once more.

Sometimes, people that don’t like you keep burning you with conjured flame, slashing you with summoned monsters, and even robbing you of your self-control, this is where Mage Slayer comes in. 

Let’s break down what this feat gives you:

  • 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. An excellent way to punish the enemy for spellcasting, whilst also hastening their defeat. In some cases, you may even drive them to less effective tactics, like melee weapon attacks, to avoid your retribution.
  • When you damage a creature that is concentrating on a spell, that creature has disadvantage on the saving throw it makes to maintain its concentration. Making a Con saving throw to maintain concentration just isn’t that hard, especially when you need to do 22 damage or more in a single blow to increase the DC at all. Imposing disadvantage can make this a bit more likely, which can cause debilitating spells like Dominate Monster to fall before you do.
  • You have advantage on saving throws against spells cast by creatures within 5 feet of you. This is a significant defensive boost against an enemy spellcaster, the only downside here being that it’s restricted to within 5 feet. Ideally, this would not be restricted by range, which would make it more generally useful and theme-appropriate.

If you’re fighting enemy mages then surely everyone wants to be a mage slayer, right? Well to some degree, yes, but for some classes and builds it may not be worth spending an ASI on:

Mage Slayer is most useful for

  • Fighters – Between having the most ASIs of any class, and a plethora of melee-centric build options, this class is very well suited to take Mage Slayer. Special mention is needed for the Battle Master subclass, which can add a maneuver to the reaction attack granted by this feat.
  • Rogues – Similar to the Fighter, having an additional ASI makes this more tempting for a Rogue, who is well suited to using the reaction attack. This is because they could potentially use Sneak Attack on the strike, which could lead to a much higher DC for the monster to maintain concentration. This would be a good option for the Inquisitive subclass, which can reliably gain Sneak Attack against a single opponent with their Insightful Fighting feature.
  • Paladin – This is primarily due to Divine Smite making the reaction attack very appealing, but it is worth mentioning that the Paladin’s Aura of Protection synergizes excellently with gaining advantage on saving throws against enemy spells. A Paladin that took the Oath of the Ancients subclass would be well suited, thematically and mechanically, to this feat due to their Aura of Warding, potentially taking only a quarter of a save-based damage spell.

Mage Slayer is least useful for:

  • Barbarians – As a MAD class this feat is just a tall order on a Barbarian, who would be better off taking a feat that better enhances their role, or increasing their stats.
  • Monks – Similar to Barbarians, Monks are so reliant on multiple stats that a feat really has to be worth it, which such an incredibly niche feat isn’t unless most encounters have an enemy spellcaster. If you do take this feat as a Monk, then using Stunning Strike on the reaction attack is recommended.
  • Fullcasters with a martial subclass (e.g. Bladesingers) – If you are using a martial subclass then your ASIs would likely be better spent on a feat to give you more hit points or make it easier to maintain your own concentration. If you do need to tangle with other casters, then you would be better served by spells like Dispel Magic and Counter Spell.

Whilst we’ve broken down who is best, and worst, suited to this feat it is strongly encouraged that you only take this feat when you know that enemy spellcasters will be a recurring obstacle throughout the campaign, for example, if you are fighting against an evil magocracy. This is because ASIs are very valuable and this feat is incredibly narrow-focused compared to most others.

We hope that you’ve found this article informative and that the person sitting next to you on the bus doesn’t have too hard a time concentrating on their crossword. If you enjoy reading about the feats in Dungeons & Dragons 5E then check out our feat spotlight section, or if you’re here because your Barbarian just got an ASI and you’re wondering what to spend it on, then check out our Barbarian guide. Until next time, good luck out there adventurers, and remember, be suspicious of any NPC with a book.