Edit: did the previous poster delete his post?
Readied Attacks are not thwarted by defensive casting, and would still be triggered. The only way to thwart a readied attack is to somehow prevent the attack from occurring at all, or prevent the attacker from perceiving you (and thus being unable to act on the cue).
Normally readied actions resolve before the action that triggers them, but there is a specific exemption for readied actions that are triggered by spellcasting and those do have the potential to interrupt the spellcasting.
So yes, two concentration checks would occur in this case.
Injury: If you take damage while trying to cast a spell, you must make a concentration check with a DC equal to 10 + the 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 the time you started and the time 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).
Yes, you can ready an attack with a trigger being 'the nemy casts a spell defensively', but the readied action always happens before the action that triggers it. So your attack is going to be resolved before the enemy casts the spell, and because of that it won't disrupt their spellcasting. They will only need to make one concentration check, for casting defensively.
EDIT: Yes, I deleted the post, because I wanted to check on something. I didn't think someone would already be replying to it. But I haven't check well enough it seems, you are right, there will be two concentration checks.
Yes, you can ready an attack with a trigger being 'the nemy casts a spell defensively', but the readied action always happens before the action that triggers it. So your attack is going to be resolved before the enemy casts the spell, and because of that it won't disrupt their spellcasting. They will only need to make one concentration check, for casting defensively.
EDIT: Yes, I deleted the post, because I wanted to check on something. I didn't think someone would already be replying to it. But I haven't check well enough it seems, you are right, there will be two concentration checks.
You need to re-read the ready action, because there are 2 parts that disagree with you.
Distracting Spellcasters: You can ready an attack against a spellcaster with the trigger "if she starts casting a spell." If you damage the spellcaster, she may lose the spell she was trying to cast (as determined by her concentration check result).
Readying to Counterspell: You may ready a counterspell against a spellcaster (often with the trigger "if she starts casting a spell"). In this case, when the spellcaster starts a spell, you get a chance to identify it with a Spellcraft check (DC 15 + spell level). If you do, and if you can cast that same spell (and are able to cast it and have it prepared, if you prepare spells), you can cast the spell as a counterspell and automatically ruin the other spellcaster's spell. Counterspelling works even if one spell is divine and the other arcane.
If you damage the caster with your ready action, it does force a concentration check. Likewise, you can ready to counterspell despite your reaction happening before the enemies.
Likewise, you can ready to counterspell despite your reaction happening before the enemies.
It should be noted that most of the time you're better off readying an action to cast an offensive spell than to counterspell. Exact match counterspells aren't reliable (no guarantee you have the same spell they're casting prepared) and Dispel Magic requires a caster level check that's little better than a coin flip. If you fail, you just wasted your turn for nothing. However, a simple Magic Missile has about the same chance of disrupting an opposing spellcaster via concentration, and even if it fails you still got off a Magic Missile. Oh, and it's a 1st level spell instead of a 3rd level spell, so big savings there.
Counterspelling is one of those things that just isn't very good. There are other rules mechanics (concentration in this case) that can achieve the same goals significantly more efficiently.
|
If they made that, then they make the concentration check for casting defensively of 15+double the spell level. If they fail that, then they trigger an attack of opportunity, which then makes them have to make another concentration check to keep the spell.
No, casting defensively means the spell doesn't provoke at all, regardless of whether you succeed at the concentration check. You're not getting attacked unless the enemy has something like the Spellbreaker feat.
However, failing the concentration check just wastes the spell with no effect. So if you have more faith in your armor class than in your concentration check, it can be better not to cast defensively.