# Casting Defensively versus Attack of Opportunity



## JoeGKushner (Feb 7, 2008)

So my buddy and I are arguing about how casting defensively interacts with attacks of opportunity.

He reads, "If the concentraction check fails, the related act also fails, with any appropriate consequences." as you lose the spell and suffer an attack of opportunity.

I read it as you DIDN'T cast the spell so provoke no attack of opportunity which is why you lose the spell.

Opinions? References would be great too.


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## Dross (Feb 7, 2008)

From the SRD Concentration skill:
The DC of the check is 15 (plus the spell’s level, if casting a spell or using a spell-like ability defensively). If the Concentration check succeeds, you may attempt the action normally without provoking any attacks of opportunity. A successful Concentration check still doesn’t allow you to take 10 on another check if you are in a stressful situation; you must make the check normally. If the Concentration check fails, the *related action also automatically fails* (with any appropriate ramifications), and the action is wasted, just as if your concentration had been disrupted by a distraction. 

The bolded part refers to preventing AoO's on the caster nothing else.

As I read it:
1: cast defensivley with concentration check #1 to avoid AoO
2: success = no AoO
3: failure = AoO, foe tries to disrupt the spell bing cast
4: AoO misses = spell goes off
5: AoO hits = Concentration check #2 to see if you can cast the spell
6: Check #2 succeeds = spell goes off
7: Check #2 fails = the spell fizzles and you loose the spell as if you had suceeded in casting.


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## skelso (Feb 7, 2008)

Actually, it can go either way.

If you are Casting Defensively, fail or not, you do not suffer an attack of opportunity.  If the roll fails, you both lose the spell and do not get to cast it.

If you cast normally (as in not defensively) and get attacked from the AoO, then you'll have to make the Concentration check to cast the spell.  Fail and you lose the spell.

It's a gamble, either way.  If you cast defensively, you might lose the spell from a bum roll, even though you may not have gotten hit from an AoO.  If you gamble that the AoO will miss, you run the risk that it actually will.  

In other words, if you're standing next to a goblin, you'd probably just want to cast normally.  If you're standing next to a bugbear, cast defensively.

From http://www.d20srd.org/srd/magicOverview/castingSpells.htm


> *Injury*
> 
> If while trying to cast a spell you take damage, you must make a Concentration check (DC 10 + points of damage taken + the level of the spell you’re casting). If you fail the check, you lose the spell without effect. The interrupting event strikes during spellcasting if it comes between when you start and when you complete a spell (for a spell with a casting time of 1 full round or more) or if it comes in response to your casting the spell (such as an attack of opportunity provoked by the spell or a contingent attack, such as a readied action).
> 
> ...




[edited for grammar]


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## Haffrung Helleyes (Feb 7, 2008)

Edit: I agree with Skelso


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## irdeggman (Feb 7, 2008)

From the PHB (more complete text than the SRD) pg 140

"Casting on the Defensive: You may attempt to cast a spell while paying attention to threats and avoiding blows. In this case you are no more vulnerable toa ttack than you would be if you were just standing there, *so casting a spell while on the defensive does not provoke an attack of opportunity.* It does, however, require a Concentration check (DC 15 + spell level) to pull off. Failure means that you lose the spell."


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## Arkhandus (Feb 7, 2008)

Yeah.  Casting defensively won't provoke an AoO, but if you fail the Concentration check, your spell fizzles because you're too focused on avoiding attacks and you mess up the spell's incantation/gestures/whatever in the process.


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## Jhulae (Feb 7, 2008)

And, if you max out concentration and have a decent Con, you eventually won't need to roll to cast spells definsively at all.  With Combat Casting and a Con bonus of +2, by 5th level, you won't need to roll for 1st level spells and by 9th level, you won't need to roll for 5th level spells.


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## Kat' (Feb 7, 2008)

Yeah, but who ever has Combat Casting, except for those classes who get it for free? 

@jhulae: isn't there a feat somewhere or a class feature (Occult Slayer from CW, maybe?) which can deny a threatened caster the ability to cast on the defense?


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## Goolpsy (Feb 7, 2008)

hmm didn't the action work like Dross described in 3.0?
and got altered in 3.5?


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## irdeggman (Feb 7, 2008)

Goolpsy said:
			
		

> hmm didn't the action work like Dross described in 3.0?
> and got altered in 3.5?





Nope. 3.0 PHB pg 125 has pretty much the exact same text.

I think people are looking at the wrong thing. That is they are looking at the Concentration skill and the specific action being attempting (i.e., casting on the defensive).


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## the Jester (Feb 7, 2008)

Kat' said:
			
		

> @jhulae: isn't there a feat somewhere or a class feature (Occult Slayer from CW, maybe?) which can deny a threatened caster the ability to cast on the defense?




Yeah, but some *ahem me* think it's overpowered. It's better than the epic feat Spellcasting Harrier.


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