If Mage Slayer activates before a spell's effects are resolved, how good is it?

[CheddarChampion]

AFAIK there is some disagreement on if mage slayer's reaction attack activates before or after a spell's effects are resolved.
But if the DM rules it happens beforehand, how good is the feat?

[Protolisk]

First thoughts, if it is used before hand, it can do damage, yes, but depending on how you understand "concentration", then are they concentrating on that spell yet? They haven't finished casting, so does it require concentration in that time? They aren't "readying" the spell as per the Ready action, and its likely their spell is taking an action or reaction to cast, so by RAW, it does not take concentration (unless they were casting it for longer than the time for an action). So there is no real ruling on if they aren't "concentrating", so it can be assumed they aren't. In this case, attacking before the spell resolves might kill them, might not, but the enemy needs no concentration check until after they cast.

If they were already concentrating, then attacking before or after is largely equal in effect.

If they had very low health, then maybe attacking first before they finish casting is good, since you can stop them from completing the cast because they died (and if there were interactions in their instantaneous spell and concentrating spell would be minimized).

So is the chance of killing them worth more than perhaps not breaking their concentration?

[CheddarChampion]

I had not considered the chance to break concentration immediately after.
I guess the idea of attacking beforehand is that even if they Misty Step away or cast Hold Person, you still get an attack (which is good on a Swashbuckler, Paladin, or the like).

[stoutstien]

I had not considered the chance to break concentration immediately after.
I guess the idea of attacking beforehand is that even if they Misty Step away or cast Hold Person, you still get an attack (which is good on a Swashbuckler, Paladin, or the like).

Personally I want to keep the reaction after the spell to keep that ablity for monster slayer. Now what would be nice is if mage Slayer had no range limit on the attack it would be a super cool feeling feat.
Take advantage of the moments right after a spell is cast to toss a hand axe at the mage.

[FrancisBean]

I just found this thread, searching before asking on the RAW thread about how Mage Slayer's timing should be interpreted. As it happens, as a DM I tend to throw larger groups of minion-grade enemies at the party, so being able to hit before the spell goes off would give a fairly strong chance of killing the caster before they finish casting. I just wish there were some clear guidance on the timing of the trigger, "casts a spell!"

[Safety Sword]

Not this again...

A trigger can not happen before the event that triggers it is resolved.

Stop it.

[ShikomeKidoMi]

Not this again...A trigger can not happen before the event that triggers it is resolved. Stop it.
Oh? What about Opportunity Attacks*? Or the Shield Spell? Or Defensive Duelist?

Obviously, triggers can resolve before the event that triggers them. The question is whether this specific trigger is meant to. I think probably not, triggers that resolve before the event generally explicitly say so. Since it doesn't explicitly say so, I think it's the version that might disrupt concentration, but won't stop a teleport or hold person from going off. It would be in keeping with how high level the Monster Slayer ability that does work first is.

*Because if you can only attack after they've finished moving out of your reach, it's entirely pointless.

[NNescio]

Oh? What about Opportunity Attacks*? Or the Shield Spell? Or Defensive Duelist?

Obviously, triggers can resolve before the event that triggers them. The question is whether this specific trigger is meant to. I think probably not, triggers that resolve before the event generally explicitly say so. Since it doesn't explicitly say so, I think it's the version that might disrupt concentration, but won't stop a teleport or hold person from going off. It would be in keeping with how high level the Monster Slayer ability that does work first is.

*Because if you can only attack after they've finished moving out of your reach, it's entirely pointless.

Well, OA does have a specific line saying "The attack occurs right before the creature leaves your reach."

I think Safety Sword was just stating the general rule. Which is to say, a reaction occurs after its trigger finishes, unless otherwise noted.

(As is the case with most rules in the D&D exception-based system — specific beats general, but that does not invalidate the general rule. Exceptio probat regulam in casibus non exceptis.)

The general rule is made clear in the DMG:


Various spells and features give a creature more reaction options, and sometimes the timing of a reaction can be difficult to adjudicate. Use this rule of thumb: follow whatever timing is specified in the reaction’s description. For example, the opportunity attack and the shield spell are clear about the fact that they can interrupt their triggers. If a reaction has no timing specified, or the timing is unclear, the reaction occurs after its trigger finishes, as in the Ready action.

(emphasis mine)

This is restated (more concisely) in Xanathar's:


If you’re unsure when a reaction occurs in relation to its trigger, here’s the rule: the reaction happens after its trigger completes, unless the description of the reaction explicitly says otherwise.

Since Mage Slayer does not provide an exception to the general rule (much less a clear one), the reaction attack occurs after the spell is cast.

[MaxWilson]

Not this again...

A trigger can not happen before the event that triggers it is resolved.

Stop it.

The question is, what if the DM rewrites the trigger? How good does the feat become?

I'd say "not that much better unless it's allowed to disrupt non-concentration spells like Dimension Door," although a Mage Slayer who poisoned his weapons with high-DC paralytic poison might be able to prevent Dimension Dooring anyway by incapacitating the target. It would still be a pretty niche feat.

If you let it disrupt non-concentration spells too, though, it becomes a specialized but still pretty awesome feat that does exactly what it says on the tin: slays mages. However, the DM would have to work out special cases like Shield spell: does Mage Slayer still activate before Shield can go off, disrupting both Shield and the main spell that was being cast?

[Safety Sword]

The question is, what if the DM rewrites the trigger? How good does the feat become?

I'd say "not that much better unless it's allowed to disrupt non-concentration spells like Dimension Door," although a Mage Slayer who poisoned his weapons with high-DC paralytic poison might be able to prevent Dimension Dooring anyway by incapacitating the target. It would still be a pretty niche feat.

If you let it disrupt non-concentration spells too, though, it becomes a specialized but still pretty awesome feat that does exactly what it says on the tin: slays mages. However, the DM would have to work out special cases like Shield spell: does Mage Slayer still activate before Shield can go off, disrupting both Shield and the main spell that was being cast?

I can only argue the common rules in the PHB and DMG etc.

If you change everything we don't have a common set of rules to analyse.

And my exasperation on this topic really comes from the 34 page thread of ridiculous arguments that were fielded years ago that could have been a 1 page question and answer if people read the rules. Not anyone here's fault. :smallwink:


Oh? What about Opportunity Attacks*? Or the Shield Spell? Or Defensive Duelist?

Obviously, triggers can resolve before the event that triggers them. The question is whether this specific trigger is meant to. I think probably not, triggers that resolve before the event generally explicitly say so. Since it doesn't explicitly say so, I think it's the version that might disrupt concentration, but won't stop a teleport or hold person from going off. It would be in keeping with how high level the Monster Slayer ability that does work first is.

*Because if you can only attack after they've finished moving out of your reach, it's entirely pointless.

A creature leaving your reach is a trigger. The Shield spell is specific about what it does. Same with defensive duelist.

They are specific cases that do what they do. You're still doing a thing when a trigger happens, not before a trigger happens.

[Slipperychicken]

If it is ruled to work like the old 3.5 AoO/spell-interruption rules, interrupting the caster's spell components to fizzle their spell, then it is really worth taking. I strongly support that kind of ruling.

Consider the "trigger" to be when the caster attempts to perform spell-components (verbal, somatic, material). If struck (by a mage-slayer, readied action, or similar) at that exact moment, the caster is damaged, so he has to roll concentration to do the components properly and make the spell come out. If the concentration fails, the components were bungled and the spell is wasted.

[Safety Sword]

If it is ruled to work like the old 3.5 AoO/spell-interruption rules, interrupting the caster's spell components to fizzle their spell, then it is really worth taking. I strongly support that kind of ruling.

Consider the "trigger" to be when the caster attempts to perform spell-components (verbal, somatic, material). If struck (by a mage-slayer, readied action, or similar) at that exact moment, the caster is damaged, so he has to roll concentration to do the components properly and make the spell come out. If the concentration fails, the components were bungled and the spell is wasted.

Well, this is pretty close to what started the aforementioned 34 page argument thread so I will expand slightly.

The D&D 5E rules don't allow you to interrupt spells with the Mage Slayer feat. The reaction attack that is granted happens after the spell is completed. The timing of the reaction isn't specified in the feat so you default to "after the trigger".

If you house rule that you can interrupt spells the feat becomes much more powerful.

[Slipperychicken]

If you house rule that you can interrupt spells the feat becomes much more powerful.

Yeah that's the point of the thread.

You don't need to burst into hypothetical/houserule discussions shouting that it isn't RAW. We all know you're very very good at rules-lawyering, so if you could just let people discuss things which explicitly aren't dnd 5e RAW, that would be fantastic.

[Safety Sword]

Yeah that's the point of the thread.

You don't need to burst into hypothetical/houserule discussions shouting that it isn't RAW. We all know you're very very good at rules-lawyering, so if you could just let people discuss things which explicitly aren't dnd 5e RAW, that would be fantastic.

Putting aside the unnecessary labelling, that's what I was doing.

It would be a feat that almost any melee combatant would want. It would reshape the dynamics of combat and providing you can get into melee combat range it would make casters almost unable to use their basic class abilities.

I think it would be a challenge to set appropriate DCs for concentration checks even. Even low level spell casters are going to have a decent chance to make the save that's usually DC 10 because you're doing low damage. At higher levels I think you'll fare much better depending on how the caster is built and whether they pump feats into making the save.

It might make playing a caster a lot less fun if it were used against player characters though.

You also then have to answer the question of whether the caster has used the spell slot or not, I guess.

[Slipperychicken]

Putting aside the unnecessary labelling, that's what I was doing.

It would be a feat that almost any melee combatant would want. It would reshape the dynamics of combat and providing you can get into melee combat range it would make casters almost unable to use their basic class abilities.

I think it would be a challenge to set appropriate DCs for concentration checks even. Even low level spell casters are going to have a decent chance to make the save that's usually DC 10 because you're doing low damage. At higher levels I think you'll fare much better depending on how the caster is built and whether they pump feats into making the save.

It might make playing a caster a lot less fun if it were used against player characters though.

You also then have to answer the question of whether the caster has used the spell slot or not, I guess.

Scaling with damage dealt should be fine? That's the way it worked before, and in 5e that's how it currently works for interrupting concentration too. Losing a spell to chip-damage feels a bit weak.

Danger from losing a spell in melee is a traditional balancing factor and tactical consideration for casters. They're supposed to not duke it out in the frontlines because someone might bonk them while they're trying to cast. Back when anyone could interrupt spellcasting with an AoO, it was a whole dynamic: enemies tried to close in on casters to disable them, warriors tried to keep enemies away from casters, and casters tried to stay out of harm's way while casting their big important spells.

It's always worked that casters waste their spell-slot if it's interrupted. The basic idea is that a spell slot is consumed when beginning to try and cast a spell, and then if the components fail (say, messing up somatic components because a goblin stuck his knife in your calf-muscle and you recoiled in pain), the slot is wasted.

Applying the change only to mage slayer means casters aren't in any danger of losing their 'basic class abilities'. They still cast with impunity around anyone else, even while grappled and restrained at 1hp. When was the last time your party even fought an NPC with mage slayer?

For the desirability of the feat after proposed changes, the feat's purpose is to give a PC a chance to shut down magicians after getting into melee. It applies to just the one enemy type (magicians), takes a reaction, and still relies on two rolls going in the character's favor -attack roll and concentration check- to actually interrupt spellcasting. It seems more like returning the spell to what a player would expect it to do, rather than making it overpowered.

[MrStabby]

How good word it be? To say the obvious it depends on the campaign.

I have just finished running a campaign with a lot of casters in of many different types. Mage slayer was a top tier feat there.

Advantage on saves vs close range spells was big by itself, concentration breaking was sometimes a big deal and a reliable reaction attack was huge. It was rogue with the feat and their ability to get close to wizards and to make awesome use of reaction attacks made it pretty brutal.

Of course it was good because the typical fight had a couple of casters in, often more. If your DM underrepresents spells as a combat tool then it is obviously a lot weaker.

[Frozenstep]

It would be a feat that almost any melee combatant would want. It would reshape the dynamics of combat and providing you can get into melee combat range it would make casters almost unable to use their basic class abilities.

Uh...no? I mean, depending on how the DM rules it, the feat could come as a surprise and interrupt something important, but otherwise, why isn't the caster just walking 5 feet away? Getting hit with the opportunity attack isn't ideal, but then they can resume casting. Even if you go so far as to grab sentinel to try to lock down the caster, you still used your reaction to attempt to stop them from moving, so you don't have one to try to stop a spell (and if they know shield, they can use that against the opportunity attack in either case).

It is still really good because it puts a lot of pressure on a caster who wants to keep concentration on something, but it's not a feat that automatically wins fights against casters for you.

[Zigludo]

We can all agree that the Mage Slayer attack can't take place before the spell, but OP seems to be asking about a theoretical homebrew change to the Mage Slayer feat. Mage Slayer is pretty widely regarded as underwhelming so I understand his motive in so doing.

The way I see it, there are two ways you could reword it - so that the attack occurs before the spell resolves, and if you wanted it to go even further, so that the attack is capable of forcing the caster to "flinch" and stop the spell from being cast. (Outside of reducing the caster's HP to 0, obviously.)

I imagine the first change would be pretty easy to write and convey. Precedent exists in the rules for similar situations like the above-mentioned opportunity attack instance. In this case, we can consider there to be some kind of declaration phase to which the player could react by saying "I use Mage Slayer" or what have you. I imagine you would just need to insert the word "before" somewhere into the ruling and most players would pick up on how the effect is meant to function without very much ambiguity. As for balance -- I think it would make the feat significantly stronger. It's often the case that when a caster is next to a melee attacker, the caster chooses to cast a spell that will directly influence the melee attacker's ability to attack the caster, be that by displacing the caster, displacing the melee combatant, debuffing the melee combatant somehow, or even dropping the melee combatant's HP to 0. In all of these cases the melee combatant would be getting one extra attack against the caster. I don't imagine it would be overpowered unless your table happens to have a whole lot of minion-type spellcasting enemies who are prone to dying when hit by a single opportunity attack, as these enemies would be basically forced to Disengage or die vs a Mage Slayer. (Which kind of suits the name "Mage Slayer", I think.)

In order to go further and let Mage Slayer interrupt casting, you would need to write additional rules to that effect in the description of Mage Slayer itself. Copy the wording of the description of concentration to say something along the lines of "Upon a successful hit, the caster must make a Constitution saving throw with DC = 10 or damage dealt. On failed save, the spell fails." Would this be overpowered? I'm tempted to say yes. (Although it's only situationally overpowered.) This, due to grappling, which is pretty hard to avoid in 5e. Having a Mage Slayer or two grappling your enemy wizard makes it so that your big caster bad guy (and this is a relatively common bad guy, I think) can have not only his spell slot wasted by a single melee attack, but, depending on adjudication, his entire turn totally wasted. So you might end up with a fight where your bad guy just stands there doing nothing while miserably having his concentration interrupted by a melee combatant that he can't even walk away from. Maybe you want that, but it seems like it might be stronger than the average feat.

[Frozenstep]

In order to go further and let Mage Slayer interrupt casting, you would need to write additional rules to that effect in the description of Mage Slayer itself. Copy the wording of the description of concentration to say something along the lines of "Upon a successful hit, the caster must make a Constitution saving throw with DC = 10 or damage dealt. On failed save, the spell fails." Would this be overpowered? I'm tempted to say yes. (Although it's only situationally overpowered.) This, due to grappling, which is pretty hard to avoid in 5e. Having a Mage Slayer or two grappling your enemy wizard makes it so that your big caster bad guy (and this is a relatively common bad guy, I think) can have not only his spell slot wasted by a single melee attack, but, depending on adjudication, his entire turn totally wasted. So you might end up with a fight where your bad guy just stands there doing nothing while miserably having his concentration interrupted by a melee combatant that he can't even walk away from. Maybe you want that, but it seems like it might be stronger than the average feat.

If your big bad guy caster is grappled, he could still cast a cantrip, take the mage slayer interrupt, then misty step out. Preferably to high ground, so he can't be easily reached.

If you're going to have an enemy wizard as your big bad guy, he/she should probably be more than a standard squishy spellcaster who stands behinds tanks and casts fireballs. Flight (without concentration, possibly), proficiency in con saves, contingency, magic items, environments they take advantage of, blink, just one thing that makes them more than an easy target. A spellcaster who hasn't taken any steps to defend themselves properly should be dumpstered by someone who specifically built themselves to kill spellcasters.

[Zigludo]

If you're going to have an enemy wizard as your big bad guy, he/she should probably be more than a standard squishy spellcaster who stands behinds tanks and casts fireballs.

Ehh, probably... Please understand that I'm really, really tempted to agree with you. And for my table if anyone asked to take Mage Slayer (nobody has) I would probably just run it all-the-way juiced up. I've actually been considering that for some time before reading this thread. But, on the other hand, I've read the MM and I've seen a few published encounters that would be pretty mucked up by a single barbarian taking this feat. I guess you can call it playing devil's advocate and meeting the developers halfway on the way they designed Mage Slayer. There are a lot of DMs out there who would be very sad to play against this and I can't bring myself to just disregard that.

[Frozenstep]

Ehh, probably... Please understand that I'm really, really tempted to agree with you. And for my table if anyone asked to take Mage Slayer (nobody has) I would probably just run it all-the-way juiced up. I've actually been considering that for some time before reading this thread. But, on the other hand, I've read the MM and I've seen a few published encounters that would be pretty mucked up by a single barbarian taking this feat. I guess you can call it playing devil's advocate and meeting the developers halfway on the way they designed Mage Slayer. There are a lot of DMs out there who would be very sad to play against this and I can't bring myself to just disregard that.

I'll take your word for it, as I haven't used the published adventures. If they love those kinds of encounters, more power to them I guess.

[loki_ragnarock]

Hot Take:

If you get the attack before the spell resolves, then the feat lives up to it's name.

It isn't called Mage Inconveniencer. It's called Mage Slayer.

If that translates to you getting to hit Mages more, then that's perfect. Whether that attack comes from them taking a step and provoking an opportunity attack before casting a spell or getting to attack them for casting a spell while adjacent, the purpose is fulfilled.

As it reads, however, a mage can cast Thunderstep and invalidate a feat. It might not have been the exact spell I wanted to cast right now. Darn.

The proposed tweak of allowing the attack to resolve before the spell completes is how the feat should read, but doesn't.


A mechanic for fizziling a spell isn't really required. Introducing such a mechanic just means that mages will take the opportunity attack to take the step away, which is great for slaying mages... but is easy enough to avoid for an intelligent opponent. Effectively wouldn't add much.

[Benny89]

I have been running a homerule that reaction attack happens BEFORE caster finish casting spell and it's very good then. Otherwise it's useless vs Sentinel or Lucky when it comes to battling mages.

So I recommend to OP to run it this way. It's especially good on Rogues and Paladins that can dish out huge burst. I had situations when enemy caster was casting a spell with Paladin in his face and he had choice of:

1. Misty Step away - useless, Vengeance Paladin would just Misty Step to him and close gap again.

2. Disengage and lose action (useless as Paladin would chase him anyway)

3. Try to cast spell in melee range.

4. Try to run away and eat Booming Blade + Smite.

So he tried to cast spell, Paladin got reaction attack + 5d8 smite and bum! dead Wizard.

I like this rulling as I think casters should be in huge disadvantage when it comes to being in melee and Mage Slayer fits perfectly into that.

Casters already are too safe in melee with Shield spell or Mirrors Image and Misty Step so anything that makes their life more difficult is welcome by me as DM.

[MaxWilson]

We can all agree that the Mage Slayer attack can't take place before the spell, but OP seems to be asking about a theoretical homebrew change to the Mage Slayer feat. Mage Slayer is pretty widely regarded as underwhelming so I understand his motive in so doing.

The way I see it, there are two ways you could reword it - so that the attack occurs before the spell resolves, and if you wanted it to go even further, so that the attack is capable of forcing the caster to "flinch" and stop the spell from being cast. (Outside of reducing the caster's HP to 0, obviously.)

I imagine the first change would be pretty easy to write and convey. Precedent exists in the rules for similar situations like the above-mentioned opportunity attack instance. In this case, we can consider there to be some kind of declaration phase to which the player could react by saying "I use Mage Slayer" or what have you. I imagine you would just need to insert the word "before" somewhere into the ruling and most players would pick up on how the effect is meant to function without very much ambiguity. As for balance -- I think it would make the feat significantly stronger. It's often the case that when a caster is next to a melee attacker, the caster chooses to cast a spell that will directly influence the melee attacker's ability to attack the caster, be that by displacing the caster, displacing the melee combatant, debuffing the melee combatant somehow, or even dropping the melee combatant's HP to 0. In all of these cases the melee combatant would be getting one extra attack against the caster. I don't imagine it would be overpowered unless your table happens to have a whole lot of minion-type spellcasting enemies who are prone to dying when hit by a single opportunity attack, as these enemies would be basically forced to Disengage or die vs a Mage Slayer. (Which kind of suits the name "Mage Slayer", I think.)

In order to go further and let Mage Slayer interrupt casting, you would need to write additional rules to that effect in the description of Mage Slayer itself. Copy the wording of the description of concentration to say something along the lines of "Upon a successful hit, the caster must make a Constitution saving throw with DC = 10 or damage dealt. On failed save, the spell fails." Would this be overpowered? I'm tempted to say yes. (Although it's only situationally overpowered.) This, due to grappling, which is pretty hard to avoid in 5e. Having a Mage Slayer or two grappling your enemy wizard makes it so that your big caster bad guy (and this is a relatively common bad guy, I think) can have not only his spell slot wasted by a single melee attack, but, depending on adjudication, his entire turn totally wasted. So you might end up with a fight where your bad guy just stands there doing nothing while miserably having his concentration interrupted by a melee combatant that he can't even walk away from. Maybe you want that, but it seems like it might be stronger than the average feat.

I don't think it would be overpowered, and my evidence is that I've actually run games before with AD&D-style spellcasting, which penalizes all spellcasting with these penalties you propose only for Mage Slayers, and additional forbids moving on rounds when you cast a spell. It actually works kind of nicely to give melee warriors with Extra Attack more of a reason for existing, instead of just playing a heavily-armored spellcaster relying on melee cantrips like Booming Blade: Attack + Extra Attack does not provoke an opportunity attack and cannot fail, but Booming Blade does and can.

If a lightly-armored BBEG enemy wizard like Emperor Palpatine? can be taken down, when surprised and away from his guards, by a judicious combination of grappling and the Mage Slayer feat... to me that sounds like a feature, not a bug. You want the PCs to have paths to victory. If the DM didn't want that approach to be viable he could have made the BBEG less of a lightly-armored wizard BBEG and more of a hybrid fighter/mage like a Demon Lord, or just made him paranoid enough that he always has bodyguards around who can do things like Shove the BBEG out of the Mage Slayer's grapple.


Ehh, probably... Please understand that I'm really, really tempted to agree with you. And for my table if anyone asked to take Mage Slayer (nobody has) I would probably just run it all-the-way juiced up. I've actually been considering that for some time before reading this thread. But, on the other hand, I've read the MM and I've seen a few published encounters that would be pretty mucked up by a single barbarian taking this feat. I guess you can call it playing devil's advocate and meeting the developers halfway on the way they designed Mage Slayer. There are a lot of DMs out there who would be very sad to play against this and I can't bring myself to just disregard that.

Why Barbarian specifically? (My first thought is Reckless Attack, but of course Reckless Attack doesn't function on Mage Slayer attacks or opportunity attacks or any other attacks not made on the Barbarian's turn.)


Casters already are too safe in melee with Shield spell or Mirrors Image and Misty Step so anything that makes their life more difficult is welcome by me as DM.

Yep, agreed.

[Zigludo]

Why Barbarian specifically?

Rage giving advantage** on Grapple + Shove was my thought process. Which then also gives you advantage on your Mage Slayer attack.

I'll also admit that I associate the feat with Barbarians in general because the idea of an 8 INT Barbarian taking the feat because of how much he hates wizards etc entertains me.

**typo

[MaxWilson]

Rage giving auto success on Grapple + Shove was my thought process. Which then also gives you advantage on your Mage Slayer attack.

By "auto success" do you mean "advantage"? Edit: okay, cool, I see your edit now--we're on the same page.

Incidentally, a Lore Bard would make the Mage Slayer even nastier: he can give Bardic Inspiration to help on the grapple check, and also Cutting Words the mage's attempt to resist the grapple.