If a mage casts a spell within 5 feat of a character with the Mage Slayer feat, does the reaction of attacking the casting character go off first, or does the spell go off first?

The Mage Slayer feat (PHB, p. 168) says:

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.

So which happens first?

Another reaction, the shield spell, says that when you are hit by an attack, you get +5 AC against all attacks, including the triggering one - but if the attack didn't hit then the reaction couldn't have been triggered. So I assume both interrupt the triggering action, and are then treated as occurring before the trigger.

  • \$\begingroup\$ Reopened - the question here isn't about whether the Mage Slayer attack can stop the spell from going off, it's about whether the attack happens before or after the spell is cast. \$\endgroup\$
    – Miniman
    Commented Jul 31, 2017 at 4:56

2 Answers 2


No, the Mage Slayer's attack takes place after the spell has been cast. From the DMG, page 252:

If a reaction has no timing specified, or the timing is unclear, the reaction occurs after its trigger finishes, as in the Ready action.

Since the trigger for Mage Slayer is when a creature casts a spell, the reaction will take place after a creature casts a spell, not as creature casts a spell.

Note that Jeremy Crawford, lead rules designer, said the same thing in his unofficial ruling.

  • \$\begingroup\$ No Jeremy Crawford made a ruling about a bonus action Misty step not a reaction. For a similar reaction refer to Sentinel feat where the opponent doesn't move after sentinel goes off. Bonus action on turn only reaction on a triggering effect. \$\endgroup\$ Commented Jul 29, 2017 at 5:34
  • 3
    \$\begingroup\$ @Billythebabygoat. The fact that the spell in question was a bonus action is irrelevant. "the spell is intended to resolve before the Mage Slayer attack" \$\endgroup\$
    – Miniman
    Commented Jul 29, 2017 at 6:06
  • \$\begingroup\$ This tweet supports interrupting a verbal spell with a readied silence spell. ie, spellcasting can be interrupted. The only question is, is a Mage Slayer reaction faster/slower than a readied Silence? \$\endgroup\$
    – Adeptus
    Commented Jul 31, 2017 at 1:21
  • 1
    \$\begingroup\$ @Adeptus Presumably, like Counterspell, such a Ready wpulld have to be triggered by a creature casting. Mage Slayer is triggered by a spell being cast. \$\endgroup\$
    – Miniman
    Commented Jul 31, 2017 at 2:49
  • 1
    \$\begingroup\$ @Adeptus J.C begins that tweet by saying "As a DM". That means that he isn't making any statement about the rules in the book allowing such a thing, just that at his table, he would let that work. \$\endgroup\$
    – Adam
    Commented Jul 31, 2017 at 12:54

No, it does not (unless it requires concentration).

Spells do what they do -- or in this case, feats do what they do. The Mage Slayer feat lets you make a melee attack against a triggering creature. It does not specify whether you do it after or before the spell resolves (general rules on reactions, to which shield is an explicit exception*, say the reaction happens after the trigger completes), nor does it specify the attack doing anything special.

Further, there are no rules about the casting of a spell being interrupted by damage, unless that spell requires concentration. Obviously, if the spell you cast does require concentration, the attack happens after you have cast it, possibly interrupting the spell immediately. (Imagine a situation where you cast a spell such as branding smite but the attack breaks your concentration before you can make the attack it enhances!)

There is also one other not obvious interaction - if you ready action the casting the spell, the rules say

When you ready a spell, you cast it as normal but hold its energy, (...) and holding onto the spell's magic requires concentration. If your concentration is broken, the spell dissipates without taking effect.

Emphasis mine. Since you cast the spell, you provoke the reaction attack from an enemy with the Mage Slayer feat.

*: Note the language 'including the triggering attack' in shield's description.


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