Hi everybody, if I have understood it correctly, when a mage casts a spell within 5 feet of a character with the Mage Slayer Feat, that character can make an opportunity attack against the mage, using her reaction, right?
What I'd like to know is: if the mage slayer deals damage to the mage with that attack, must the mage make a Constitution save in order not to lose the spell or the Concentration or not? I'd say yes, but I'm not sure about it.
What do you think?
Many thanks, and I apologize if this issue has been treated before or in another post, but I haven't seen it.
Happy life and happy gaming,
Fenn Grunberg
If the spell has a duration of Instantaneous, I don't believe it can be disrupted by Mage Slayer (because there is no concentration check involved with spells of that duration).
If the spell has a duration entry that specifies Concentration, then yes you can potentially disrupt it as you described with a Mage Slayer OA. The reaction is an instant response to a trigger. The mage casting the spell is the trigger for Mage Slayer. Taking damage while trying to concentrate on a spell (for spells with duration Concentration) forces a CON save to maintain your concentration, which is made at disadvantage because of the Mage Slayer's second bullet point.
See "Duration" under Spellcasting (Base Rules p.79-80).
You could stop an Instantaneous spell with the Counterspell spell, though.
Oh man, a tag-team Bard and Monk combo. Bard counterspells while the Monk wrecks any spellcaster's day. And he has the mobility to get to him...
Theres also the question on if your attack, being a reaction, goes before he finishes casting the spell, like is being debated in the Sentinel Feat. One creator tweets yes, the other no.
I'd say that there is one of two cases, but both have two parts:
- The attack "comes first" and can stop a spell from occuring if it kills (or incapacitates) the caster. If so, the attack cannot also force a constitution saving throw disrupt a concentration spell being cast.
- The attack can interrupt a concentration spell as it is cast (the attack comes after the spell), but in this case, if the attack kills or incapacitates the caster, it doesn't stop any instantaneous effect of the spell.
Regardless of which approach adopted, I would be consistent and apply both parts: either you can incapacitate a wizard to stop her fireball with Mage Slayer, or you can stab a spellcaster to ruin his concentration on a haste spell as he casts it, but the two are mutually exclusive rules interpretations.
One thing to be aware of is that Mage Slayer does not grant an opportunity attack. It lets you make a melee weapon attack as a reaction, but it's not actually an opportunity attack, it's just a normal melee attack. This doesn't seem like a big difference, but it can be important: if you have both Mage Slayer and Sentinel, for example, the reaction attack granted by Mage Slayer doesn't reduce the target's speed to 0, so the mage you just slayered can still move away from you afterward without penalty (especially since you've already used your reaction for the round).
JRutterbush wrote: