# How Many Concentration Checks?

### Rules Questions

I'm sure this has been answered here before but I can't seem to find a thread that addresses this specifically.

So, you are a Wizard and you try to cast a spell. Unfortunately you are also on fire, bleeding, have magical acid on you, and you just took an attack of opportunity from someone standing next to you when you tried to cast. How many concentration checks do you have to make?

I think the answer is four, one for each ongoing effect and another for the AoO, but then again it might just be two, if you take all the ongoing effects together and then add in the AoO.

I think it's only 2, but I could be wrong.

Of course if it IS only 2 that's probably a very high check for the continuous damage.

What makes me thing you need to make four is because in the rules specify making a roll against a source, but it is somewhere ambiguous. It says:

If you are taking continuous damage...You must make a concentration check with a DC equal to 10 + 1/2 the damage that the continuous source last dealt + the level of the spell you’re casting.

It seems like you could read this either way, but some clarification must have been made on this at some point.

Probably 4, going by the text.

It's a little weird that taking 1 damage from each of 40 sources is trivial to concentrate through but taking 40 damage from one source is nearly impossible, though.

Chrion wrote:
but some clarification must have been made on this at some point.

<sweet_summer_child.gif>

Man I didn't realize my last post was just riddled with typos and i can't fix it now. Arg! Anyway...

blahpers wrote:
It's a little weird that taking 1 damage from each of 40 sources is trivial to concentrate through but taking 40 damage from one source is nearly impossible, though.

Even taking only one damage you would need to be pretty high level to make this an autopass. The lowest the DC can be is 11 if you are casting a 0 lvl spell. So to make this an automatic success you would have to have at least a caster level of 10. But even you pass the check on everything but the roll of a 1, if you did really have to roll 40 times, chances are you are going to roll a 1 somewhere in those 40 rolls. In other words, even if the DC is low, having to make more rolls against it increases the chance of not passing, so if you are trying to stop an enemy spellcaster, it is beneficial to the players if the enemy has to make multiple rolls. On the other hand, having to pass one really hard check is also...really hard. So adding the ongoing damage together doesn't make things super easy either.

Hopefully there is a real answer to this but if blahpers doesn't know...to whom are we to turn?

Concentration checks also include your casting stat mod, so which makes that DC 11 an auto pass at around level 5 or 6.

Java Man wrote:
Concentration checks also include your casting stat mod, so which makes that DC 11 an auto pass at around level 5 or 6.

Oops! Yes you are right. But, again, that is the easiest possible scenario.

Bumping this to hopefully get more eyes on it.

Related question - how many concentration checks do you make if hit by magic missiles?
General consensus seems to be that you must make one check for each separate thing that damages you. However, with a spell that causes multiple projectiles to hit you, the projectile damage is combined into one.

Chrion wrote:
But even you pass the check on everything but the roll of a 1, if you did really have to roll 40 times, chances are you are going to roll a 1 somewhere in those 40 rolls. In other words, even if the DC is low, having to make more rolls against it increases the chance of not passing, so if you are trying to stop an enemy spellcaster, it is beneficial to the players if the enemy has to make multiple rolls. On the other hand, having to pass one really hard check is also...really hard. So adding the ongoing damage together doesn't make things super easy either.

I do not see anything saying that rolling a 1 on a concentration check is a failure.

Nat 1 is auto fail on a save and on an attack, but I don't see it listed for concentration.

/cevah

Cevah wrote:
Chrion wrote:
But even you pass the check on everything but the roll of a 1, if you did really have to roll 40 times, chances are you are going to roll a 1 somewhere in those 40 rolls. In other words, even if the DC is low, having to make more rolls against it increases the chance of not passing, so if you are trying to stop an enemy spellcaster, it is beneficial to the players if the enemy has to make multiple rolls. On the other hand, having to pass one really hard check is also...really hard. So adding the ongoing damage together doesn't make things super easy either.

I do not see anything saying that rolling a 1 on a concentration check is a failure.

Nat 1 is auto fail on a save and on an attack, but I don't see it listed for concentration.

/cevah

Right, I wasn't trying to argue that. What I meant was that, there are situations where you will beat a DC if you roll anything other than a one, but fail when you roll a one, not because it is a crit fail, but because it is the only number where your bonuses plus roll of a one wouldn't be enough to pass the DC.

Matthew Downie wrote:
General consensus seems to be that you must make one check for each separate thing that damages you. However, with a spell that causes multiple projectiles to hit you, the projectile damage is combined into one.

This is a pretty good conversation about the topic. It's too bad it got muddled by Magic Missle. All three missiles hit simultaneously so even though you roll for each they all "impact" at the same time, thus the need for only one roll would make more sense.

Chrion wrote:
But even you pass the check on everything but the roll of a 1, if you did really have to roll 40 times, chances are you are going to roll a 1 somewhere in those 40 rolls. In other words, even if the DC is low, having to make more rolls against it increases the chance of not passing, so if you are trying to stop an enemy spellcaster, it is beneficial to the players if the enemy has to make multiple rolls. On the other hand, having to pass one really hard check is also...really hard. So adding the ongoing damage together doesn't make things super easy either.

Generally speaking, one high DC concentration check is going to be a lot harder to pass than a bunch of easier ones.

Let's say we're targeting this guy, a level 9 wizard with an unimpressive +13 concentration. He's casting a level 4 spell.

He passes concentration on a 2 (DC 15) if he takes 1 point of damage. If you somehow hit him 20 times for 1 point of damage and the GM makes him roll 20 checks, he has about a 65% chance of failing at least one roll.

If we treat it as a single hit for 20 points of damage, it becomes a DC 34 check. This is impossible for him to make.

If we hit him three times for 5 points of damage, he needs to roll a 6 three times. He has about a 58% chance of failure.

If we hit him once for 15 points of damage, he has a 75% chance of failure.