Mage Slayer 5e

Published on June 2, 2022, Last modified on September 28th, 2023

Mage Slayer is an attractive feat for martials who want to make life tough for enemy spellcasters. Unfortunately, an update to D&D’s system hurt it’s viability. Learn more here.

Victor Adame Minguez - Wizards of the Coast - Tenth District Legionnaire

Arcane Eye may earn a small commission from affiliate links in this article. Learn more.

What Is Mage Slayer 5e?

Spellcasters are well known to be very powerful in D&D 5e, as the limits on martial classes is huge in comparison. One of the few feats given to even the playing field is Mage Slayer, a feat that lets martial classes beat up those spellcasting nerds.

How Does Mage Slayer Work?

Once you’ve picked this feat up, you get three new benefits:

You gain advantage on saving throws against spells cast by creatures within 5ft of you.
When you damage a creature that is concentrating on a spell, they gain disadvantage on their saving throw to maintain it.
If a creature within 5ft of you casts a spell, you may use your reaction to make a melee weapon attack against them.

Is Mage Slayer Good?

We gave Mage Slayer a C Tier rating In our 5e Feats Tier List, making it a below-average feat in D&D 5e.

Unfortunately, with the changes to monster stat blocks made post-Oct. 4th, 2021 update, Mage Slayer has received a massive nerf. Most spellcasting creatures (other than player characters) got their spell list greatly reduced and now rely on “spell-based actions” to do damage and perform other effects that used to be spells. Jeremy Crawford confirmed that these melee/ranged spell attacks do not trigger counterspell because they don’t count as spells. Therefore, they won’t trigger Mage Slayer’s reaction.

Mage Slayer can be still be a worthwhile feat if:

You’re playing in a campaign with tons of spellcasters (i.e Strixhaven)
Your DM prefers to use pre-Oct. 4th, 2021 update stat blocks
Your DM rules that spell attacks count as spells for Mage Slayer’s effects

With this said, we have dropped the rating of Mage Slayer from a B Tier to a C Tier to reflect the nerf. Because the ratings for Mage Slayer vary so wildly, it’s best to pick this up after you’ve played a couple of sessions to see what kind of enemies you’re up against. Builds that get a feat at 1st level, like variant humans, would certainly rather pick up a feat they know will make an impact on their day-to-day play.

Mage Slayer 5e Interactions

Naturally, players can make some challenging interpretations of the rules since spellcasting is so complex at times. Here are some common interactions you may need to know about:

If a spell were countered by counterspell, Mage Slayer would trigger, as the spell was still ‘cast,’ but nothing happened.
If a spell was cast that moves the caster (like misty step), the caster has already moved before a player can make a reaction. For more information on this, check the DMG p.252.
Those with Mage Slayer need to be able to see or hear a spell being cast to use their reaction, meaning using Subtle Spell won’t trigger it.
Having a weapon with reach doesn’t increase the range of Mage Slayer’s reaction; they still need to be within 5ft.
Spell attacks (i.e spell effects that aren’t listed as spells in a sourcebook) do no trigger Mage Slayer’s effects.

Which 5e Classes Make the Most of Mage Slayer?

The color code below has been implemented to help you identify, at a glance, how good the Mage Slayer 5e feat is for a specific class/subclass.

Red isn’t going to contribute to the effectiveness of your character build at all
Orange Situationally good, but a below-average option otherwise
Green is a good option
Blue is a great option, you should strongly consider this option for your character
Sky Blue is an amazing option. If you do not take this option your character would not be optimized

Mage Slayer is best on builds that:

Want to be on the front lines, usually damage-dealers or those with high mobility to get to the casters in the back.
Have the ability to stay close to spellcasting enemies.
Don’t have a potent reaction already available, like Sentinel or counterspell.
Are in high magic campaigns with plenty of spellcaster enemies.

Artificer: This feat can be handy depending on which subclass you take. Battle Smiths, in particular, want to be in the thick of it and get some hits in, same with Armorers with the Guardian armor. However, it's a pretty build-dependant feat, and artificers are incredibly diverse.

Barbarian: If you're facing spellcasters in most combats, barbarians will enjoy what this feat has to offer. Barbarians offer some of the most mobility and durability in the game, and they love to output more damage. Otherwise, this spell falls behind feats that will be useful in every combat, like Great Weapon Master.

Bard: I’d find it hard to think of a bard who would value this feat. Most bards are not in the front lines; they don’t typically want to spend their turns in melee range unless they need to. College of Valor and College of Swords can use this feat but need to make sure they can survive the frontlines.

Cleric: Clerics that are focused on melee damage, like War Domain and Forge Domain, definitely can use this feat. It isn’t essential on these subclasses, but it packs a powerful punch. Other domains are better off with supporting feats.

Druid: The only melee druid builds are those who take the Circle of the Moon, and the rest should just stop reading here. Moon druids can use this feat to a pretty good degree, as it can still trigger while in Wild Shape.

Fighter: Almost all fighters can benefit from this feat, as long as they are playing in a campaign with plenty of spellcasters. Almost all fighters excel in melee combat, and they have excellent damage output. There isn’t one in particular that stands out, though. Just remember that most fighters have access to a few different reactions to choose from, and you only get one reaction per round.

Monk: While most monks can benefit from this feat, I wouldn't say it's all that. Monks get a lot of reactions to use, and most of them are pretty helpful in most scenarios. If you want tons of options at all times, this is for you.

Paladin: As long as you have plenty of spellcasters in your campaign, paladins can make great use of Mage Slayer. As most paladins are frontline warriors with access to their own magic, it makes them great candidates to close in on enemy casters. It's important to note that you can smite with the reaction, meaning you can easily take out tough casters with ease.

Ranger: Most rangers find themselves in between melee and ranged combat, making this feat tough to recommend. If you plan to stay in mostly melee, it's a good pick. Otherwise, it's underwhelming.

Rogue: This can be a good option for most rogues, but there isn’t a particular subclass that can make the most. Players who want to keep casters at bay or takedown important targets definitely want this.

Sorcerer: Sorcerers don’t want this. They should seldom be attacking with melee weapons.

Warlock: Most warlocks are going to want to skip this. The only exception is hexblades, which can sneak in some extra damage, but I wouldn’t call it essential.

Wizard: Wizards are just too squishy for the frontlines. Bladesingers are a little beefier, but I would skip this feat in place of something with more flexibility.

Mage Slayer 5e FAQs

Does Mage Slayer interupt a spell?

This feat doesn’t stop a spell from being cast, only checking if a spell was attempted to be cast. It does have the chance to break concentration though if they fail the save.

Does having a longer reach extend Mage Slayer's reaction?

No. You will still need to be within 5 feet of the creature casting the spell in order to trigger the reaction.

Do I have to see the spell being cast in order to use Mage Slayer?

Yes. You need to have visual cues that a creature has cast a spell in order to use Mage Slayer's reaction.

Do spell attacks trigger Mage Slayer's effects?

No. Spell attacks are not 'spells' and therefore don't trigger Mage Slayer's reaction, nor their advantage on saving throws if the enemy is within 5 feet.

Does Mage Slayer work with Sentinel?

The Sentinel feat is all based around attacks of opportunity, while Mage Slayer is checking for spellcasting and providing an attack against them. The only way these interact is that you can better disrupt their concentration when you hit an enemy with the opportunity attack.

Conclusion

Mage Slayer used to be a stellar feat, but the nerf in Oct. 2021 really hurt its viability. As it stands, it can still be beneficial depending on your campaign. It might not fit every build, but martials who want to foil spellcasters can make excellent use of the potent effect it provides.

Mike Bernier

Mike Bernier is the lead content writer and founder of Arcane Eye. He is a Adamantine best-selling author of Strixhaven: A Syllabus of Sorcery on DMs Guild and is a contributing author at D&D Beyond. Follow Mike on Twitter.