Interrupt the casting of a spell

[CalamaroJoe]

I only recently made a few considerations on spells and concentration. For me the topic is quite new, so I ask for the Playground experience to help me understand.

If MageA spent a few points on Concentration, plus the Combat Casting feat, he is never going to fail the check for casting on the defensive (excluding natural 1s). So he never provokes AOO.
Has WarriorB any chance if interrupting the spell other than readying an attack?

Then, if the readied attack scores an hit, MageA must make a concentration ckeck with DC = 10 + spell level + damage dealt.
But if MageA has 2 or more opponents that ready their attacks, and they hit, how is the concentration check handled? Must (s)he succeed 2 (or more, depending on the attacks) checks, or only one check with all the damage received? The SRD tells "Damaged during the action", so it seems that it must all be added up...

Another thing:
If WarriorB readies an attack but then MageA doesn't cast on the defensive (thus provoking AOO), which attack takes place? The readied, the AOO, WarriorB's choice?

[Yora]

1: I say each time you take damage, you have to macke a Concentration check. There are many ways in which several attackers can hit a caster and since the DC is dependent on the damage of an attack, there's nothing that suggests you'd pick which of the damages you take affects the DC, or how to combine damages into one DC. So one check for every hit it is.

2: There's nothing in the rules about multiple readied actions or attacks of opportunity at the same time. But a common rule that is often applied is that you always apply effects in the order most beneficial to the character. Since you can usually make only one AoO per round, it seems to be best to first make the readied action and then decide if you also want to make an AoO. If you first make your AoO and then realize you don't want to make a second attack, your readied action is wasted and you can't make another AoO in that round.

[NNescio]

I only recently made a few considerations on spells and concentration. For me the topic is quite new, so I ask for the Playground experience to help me understand.

If MageA spent a few points on Concentration, plus the Combat Casting feat, he is never going to fail the check for casting on the defensive (excluding natural 1s). So he never provokes AOO.
Has WarriorB any chance if interrupting the spell other than readying an attack?

Then, if the readied attack scores an hit, MageA must make a concentration ckeck with DC = 10 + spell level + damage dealt.
But if MageA has 2 or more opponents that ready their attacks, and they hit, how is the concentration check handled? Must (s)he succeed 2 (or more, depending on the attacks) checks, or only one check with all the damage received? The SRD tells "Damaged during the action", so it seems that it must all be added up...

Another thing:
If WarriorB readies an attack but then MageA doesn't cast on the defensive (thus provoking AOO), which attack takes place? The readied, the AOO, WarriorB's choice?

Skill checks do not auto-fail on a natural 1. Neither do they auto-succeed on a natural 20.

Multiple attacks= multiple distractions= multiple concentration checks. This is consistent with how Damage Reduction and Massive Damage are handled. (not that anyone uses the latter.)

AoO first (which you can choose not to take), then the readied action (assuming he didn't lose the spell from the AoO).

[Feytalist]

I'm pretty sure most DM's allow natural 1's to fail and natural 20's to succeed on skill checks as well. I know mine does.

That's how you get those awesome bluff moments.

It's pretty difficult to interrupt a spell that takes only a standard action to cast. It boils down to readied actions, ongoing damage and environmental effects (the last two of which is not cancelled by defensive casting).

For full-round spells, every single successful attack made against the mage needs a Concentration check.

By the way, does Combat Casting increase the Concentration check against those attacks as well?

[Thurbane]

I'm pretty sure most DM's allow natural 1's to fail and natural 20's to succeed on skill checks as well. I know mine does.
It does seem to be a pretty common houserule, in my experience.

There's a feat that prevents anyone from casting defensively within your threat range...Mage Slayer.

[2xMachina]

RAW it does not, but if you want to houserule it...

However, I see problems in that people can succeed in anything after 20 tries.

EDIT: Mage killer? 5' step back. (You need the stance Island of Blades too, else, it's less useful)

There are also ways to take 10 concentration, which gets very useful if you auto-fail with a 1.

[Thurbane]

However, I see problems in that people can succeed in anything after 20 tries.
The rule we use in some games is that a natural 1 equals -10 to your check, while a natural 20 equals +10. That way, someone skilled enough in a skill doesn't autofail on a 1, while still giving someone a small to chance to succeed on a very difficult roll.

EDIT: Mage killer? 5' step back. (You need the stance Island of Blades too, else, it's less useful)
True, but that often depends on the terrain of the battle, and the reach of the character with Mage Slayer.

Another tactic for casters to overcome Mage Slayer is to take ranks in Tumble, so the can tumble out of threat range (without provoking an AoO) before casting. I find that Mage Slayer is mostly to get the element of surprise the first time an enemy tries to cast defensively while near you. Even one spell they don't get off is to your benefit.

[Feytalist]

However, I see problems in that people can succeed in anything after 20 tries.

Theoretically yes, but it's more a randomness factor than anything else. Most skills you are not allowed to retry, so the chance of you going "ok, everything up until 19 didn't work, lets try 20" is very slim.

In the heat of the moment, a natural 20 is more like "due to extraordinary circumstances, you actually manage to do this impossible feat", which is what makes the game great.

I would love to see a tumbling mage in action :smallbiggrin:

[Cyrion]

With readied actions, if your opponent does not do what you have readied your action for, your action is wasted for the round. That doesn't change if something he does grants you an attack of opportunity. Thus, it pays to be as general as you can when you specify what you're readying for.

If you say "I'm readying an attack to try to interrupt the spell if MageA casts defensively" gets too specific when "I'm readying an attack to try to interrupt the spell if MageA looks like he's casting a spell" will accomplish the same thing with more flexibility.

[CalamaroJoe]

Thanks everybody for the answers :smallsmile:


It's pretty difficult to interrupt a spell that takes only a standard action to cast. It boils down to readied actions, ongoing damage and environmental effects (the last two of which is not cancelled by defensive casting).


There's a feat that prevents anyone from casting defensively within your threat range...Mage Slayer.

These are good suggestions. They will be useful when my mage PCs encounter clever enemies. Also if a melee opponent with just this right feat can be regarded as a mean blow :smallamused:


Skill checks do not auto-fail on a natural 1. Neither do they auto-succeed on a natural 20.

Oh, I see

[Gadora]

The rule we use in some games is that a natural 1 equals -10 to your check, while a natural 20 equals +10. That way, someone skilled enough in a skill doesn't autofail on a 1, while still giving someone a small to chance to succeed on a very difficult roll.

True, but that often depends on the terrain of the battle, and the reach of the character with Mage Slayer.

Another tactic for casters to overcome Mage Slayer is to take ranks in Tumble, so the can tumble out of threat range (without provoking an AoO) before casting. I find that Mage Slayer is mostly to get the element of surprise the first time an enemy tries to cast defensively while near you. Even one spell they don't get off is to your benefit.

How are you getting anelement of surprise out of Mage Slayer? Threatened casters are aware that they can't cast defensively when threatened by a character with Mage Slayer. If you want to get good use out of the feat, you really need to have some reach.

[Ravens_cry]

It does seem to be a pretty common houserule, in my experience.

It may be a common one, my group uses a +10, -10 variation, but I do not like it.

[Kyberwulf]

Well with the Nat 20 or, Nat 1 my house rule is that if its a 20, they get to reroll a 1d20 and add it to their number.. no modifiers add to the bonus roll. straight up d20
and if its a 1 its treated as a fumble, and they make a dc save. The Save depends on the action... like trying to use a social skill... they make a will save or the other party convinces them of their point of view...if they where tumbling..a ref save or the fall on their face...

On the Reading an action, One of my player usally says.. "if the mage does something supicious i trip him" which... reminds me, i was gonna ask. What happens when you trip a mage casting a spell? and.. can a mage still cast spells when he is laying down?

And have the monk/warrior punching the mage using Stunning fist?

[2xMachina]

I suppose he takes a Concentration check for violent movement.

If he passes, he casts as normal. Nothing stopping them from casting while lying down.

[Thurbane]

How are you getting anelement of surprise out of Mage Slayer? Threatened casters are aware that they can't cast defensively when threatened by a character with Mage Slayer. If you want to get good use out of the feat, you really need to have some reach.
Ah, I see..I had missed the description in the feat that indicates they already know they can't cast defensively.

A Knight with some reach (Deformity: tall or Inhuman Reach, reach weapon, Belt of Growth etc.) could get some good use from Mage Slayer...

[NNescio]

I'm pretty sure most DM's allow natural 1's to fail and natural 20's to succeed on skill checks as well. I know mine does.

That's how you get those awesome bluff moments.

Doesn't that lead to silliness like... an archmage failing to recognize a cantrip, a master blacksmith failing to smith a simple iron nail, trained knights falling off their saddles every few minutes, and... a commoner jumping to the moon?

And let's not get into Knowledge checks...

Not that RAW itself isn't already silly in a lot of places, but a houserule which makes things sillier seems to be a bit less than sound to me.