Cometary Collision vs a Large opponent's AoO

So I have this situation: Largo the Large, who is Large (and a humanoid, so he gets reach), charges Count Countercharge, who has readied his Cometary Collision feat, and is Medium-sized.

The question is: does Largo, RAW, get an AoO on the Count?

The reasons I would think not are:

1. I seem to recall that you cannot take an AoO on your own turn, but I can't find where I got that from.

2. Is an AoO during a charge possible? I think not - again, I can't source why.

• Does Largo the large have reach or armed with a reach weapon? (Being Large doesn't automatically give a creature reach.) Likewise, does Count Countercharge have reach? – Hey I Can Chan Feb 25 at 2:04
• Large should give reach. He doesn't have a reach weapon otherwise, and neither does Count. – ThanosMaravel Feb 25 at 8:14
• If Largo is Large (long) instead of Large (tall) like a brown bear, he won't have reach. (Also see Table 8–4: Creature Size and Scale (Player's Handbook 149).) Could the question be edited to include those details? – Hey I Can Chan Feb 25 at 11:39
• Hey, good catch! Added. – ThanosMaravel Feb 26 at 8:51

Largo can, in fact, take the attack of opportunity. Nothing says you can only take attacks of opportunity when it is not your turn, and nothing says you cannot take an attack of opportunity while doing something else. Attacks of opportunity are not actions, so one occurring in the middle of a full-round action like charge is permissible.

It’s impossible to prove a negative, but the rules on attacks of opportunity simply mention nothing of the sort.

1. The word “turn” is only used three times, and all for explaining how attacks of opportunity interrupt a turn, and after one is resolved that turn continues. The rules do say that you can perform an attack of opportunity “even when it is not your action,” (emphasis mine), but the word “even” here indicates that this is an inclusive statement, not an exhaustive one—you can do so “even” when you might otherwise expect you couldn’t. That implies that not only you can when it is “your action,” but that this is considered by the author to be the more expected case (and indeed, for other combat happenings, it would be).

2. The word “action” is used eleven times—once in the above quote about attacking “even when it is not your action,” and then ten times to describe various sorts of actions that provoke. Note the unusual phrasing “your action” to indicate your turn—this was common early on in 3.5e, and was avoided in later books as it was confusing.

So anyway, the flow here would be that Largo begins to charge, triggering the Count’s readied action. That interrupts Largo’s charge, and begins the Count’s charge. When the Count begins to close from within 10 feet of Largo to within 5 feet, he provokes Largo. That interrupts the Count’s charge, allowing Largo to take an attack of opportunity. Once Largo has done that, the Count’s interrupted charge resumes, and the Count moves adjacent to Largo and attacks with the relevant bonuses. With that resolved, Largo’s own action resumes, allowing Largo to either hit Count or continue his charge on to his original target (providing Count is not in the way now).

If we wanted to make this more ridiculous, we could have Largo take his attack of opportunity with an unarmed strike but without Improved Unarmed Strike—causing him to provoke the Count, who would get an attack of opportunity before Largo got to complete his. The rest of the events would resolve the same.

You can take actions in the middle of another action, but any action other than a free action ruins the remaining portion of your initial action.

Relevant rules part here is:

Free Action
... You can perform one or more free actions while taking another action normally...

Now if it has to be pointed for free actions it means you can't generally take another action normally while you perform another action.

Some examples: you end your movement when you attack and remaining portion is wasted, if you do something while you cast a spell it fizzles, you can't continue full-attack after you move your speed in the middle of it even if you have additional move action on your turn. Some of those examples can be changed with exceptions, but an existence of exceptions only strengthen general prohibition.

So for your example Largo can take an attack of opportunity, but then he can't continue his charge. Or he can avoid using attack of opportunity and either continue his charge if path isn't now blocked or attack Count as if he charged him if Count is in the way.

Also, some people may say attacks of opportunity aren't actions. Sure they lack action type. But consider dazed creature, the only effect of the condition being: "a dazed creature can take no actions". Would you allow it to make one?

Attacks of opportunity are also listed as an exception here:

The Combat Round
... When a character’s turn comes up in the initiative sequence, that character performs his entire round’s worth of actions. (For exceptions, see Attacks of Opportunity and Special Initiative Actions.)

meaning they are also actions, but aren't performed on a character’s turn.

• Huh. So, for example, Abe could ready the action Drink a potion with the trigger After my foe's made its second attack so as to provoke an attack of opportunity from the foe in the midst of the foe's attack routine therefore forcing the foe to make a choice between either finishing its routine or making that attack of opportunity? That opens up some tactical options, I guess, but it also sounds difficult to manage. – Hey I Can Chan Feb 26 at 20:37
• @HeyICanChan To be honest, I'm really interested in feedback on this answer. I myself not totally satisfied with my wiev on the subject, and would appriciate being corrected at some point. Be I a DM I'd consider it twise to apply my ruling from this answer in unmodified way. But first, i'd like to awoid modifications of existing rules when possible (maybe someone will prove me wrong, things function differently, and there will be no need to modify anything). And second, in the text TS asks for RAW, even if there is no raw tag. – annoying imp Feb 26 at 21:16
• That's fair, and I'd offer some feedback, but first I want to be clear on my understanding of the answer, hence my example in the comment. A broader question would be This answer seems to make attacks of opportunity carry more weight in the action economy because attacks of opportunity are not given an action cost. Is that accurate? You can, of course, opt to address both of my questions or neither. :-) – Hey I Can Chan Feb 26 at 22:24
• @ThanosMaravel And that's totaly fine. I just felt like I should point that issue to you, but if you find another answer more convincing - use it. And have fun in your games. – annoying imp Feb 28 at 8:20
• The attack of opportunity and readied action rules explicitly state that any interrupted action resumes after the interruption is resolved. Your claim that non-free-action interruptions prevent the rest of the interrupted action from resolving is incorrect. – KRyan Mar 2 at 20:35