Attacks of Opportunity in depth (with example pictures)
Soooo, there are a few assumptions in D&D. One is that weapons are one of the most important things in combat. Another is that a character actively engaged in a combat is aware of things happening around him and can defend himself even if not explicitly stated, and can react to anything around him. A major one is that although everything is happening at once in the 'real' combat, everyone playing will accept the suspension of disbelief that you resolve combat using turn-based rules.
As stated, it's hard to suspend disbelief when this leads to a few silly happenings. Can a creature really thump you with a weapon then run away without your character counter-attacking? Would you really stand there while a spellcaster prepares a fireball to blast you and not try to stop him? Infact, if someone is standing around not regarding you, would you really not try to hit him?
So there is an idea that despite the normal turn based rules, if someone in combat is not focused on the opponents around them, those opponents can interrupt normal play with a basic attack - the Attack of Opportunity.
You can only get one attack of opportunity per round unless you have a specific feat allowing you more. Even then, you can only make one attack per 'offense' against an opponent. The attack must be a basic attack - just your weapon in your hand. No spells, no ranged weapons, no weird abilities. You are literally reflexively thumping them at a vulnerable moment, no thought. The good news is that this attack used your full melee bonus, and you get to make the attack even if you have attacked in your own turn, and you can still attack after if you turn has yet to come up. The better news is that the attack of opportunity interrupts the triggering action. So you might knock the run-away unconscious before he moves, you might disrupt or even kill the spellcaster before he gets his shot off!
In order to be vulnerable to an attack of opportunity, you have to be in a square threatened by an opponent. All things being equal, an opponent with a weapon of any kind threatens all eight squares around him.
Now, the good news is that if an opponent is unarmed, he cannot threaten the squares around him (due to his limited reach).
Five basic things provoke an attack of opportunity:
1. Moving
out of a threatened square. As said, the assumption is that you are focused and defending yourself normally. Therefore, you can happily move within an opponent's range without him lashing out. However, if you turn and run, of if you try and move passed him once you get in his range, you are pushing your luck!
There are two important ways to avoid incurring an attack of opportunity by moving. The first is the
five foot step. If you make no other movement in combat, you can take a single step into another square. This assumes you are still engaged with everything around you, and is a small tactical move.
The second way to avoid taking an attack of opportunity is to use a
withdraw.. This is a fullround action - so you cannot take a standard action. If you declare it, you may move out of a threatened square without taking an attack of opportunity. You may then carry on moving, taking up to twice your movement in total. However, any further steps will provoke attacks of opportunity if applicable.
2. Doing something not related to the combat around you. If you try to drink a potion, rummage in your backpack, use your perception to check outside of the battlefield, etc you
will be vulnerabe to an attack of opportunity.
3. Casting a spell or using spell-like ability. Anything really that requires concentration to before leaves you temporarily vulnerable. For spellcasters, taking damage when spellcasting can disrupt the spell. They will usually need to make a concentration check, with a difficulty including the damage taken, to complete the spell.
4. Doing some complex in combat. Trying to trip someone up, smash a weapon, grab hold of an enemy, etc all leave you open to retaliation before you can do your cool effect. Note that firing a ranged weapon, due to its complex nature of aiming and firing, also counts and leaves you vulnerable!
5. Making an unarmed strike. If you try to attack someone who is armed, when you yourself are not armed, you provoke an attack of opportunity. As you can imagine, if you need to get in closer to them to make the hit, then they can easily take a poke at you.
Anyway, so the Trolin combat was made simple due to the close proximity of everyone, and the fact most people were unarmed. However, the Trolin did dive for a club... so, assuming he had grabbed hold of the club, and did threaten the indicated squares, then he would have threatened the squares of Ameena, Westian, and Haynuus, though not Falkor. As Westian and Ameena were unarmed, had the Trolin possessed a club, those two would have been vulnerable to attacks of opportunity if they tried to attack. Haynuus, possessing a weapon, could always attack without incurring an attack of opportunity.
Falkor, despite casting spells close to the Trolin, was not casting spells in a square threatened by the Trolin. Hence he provoked no attacks of opportunity.
So, the question is, had the Trolin done the move below, what would have happened?
The answer...nothing! The main reason for this being the Trolin had only moved 5 foot - tactically, he would still be cautious enough. Also, Ameena and Westian could not generate attacks of opportunities, being unarmed, and Falkor could not generate one, as the Trolin moved into a threatened square, not out of one.
However, let's imagine the Trolin was able, and willing, to move two squares across to be adjacent to Falkor (walking through a wall). What would happen?
In this case, Ameena and Westian are still helpless, because of their lack of weapons. However, Haynuus can now make an attack of opportunity!Because you cannot 'five foot step' with another movement, the Trolin no longer gets his first square 'for free'. So he moves out of Haynuus's corner threantening square, potentially provoking an attack, then moves out of Haynuus's adjacent threatening square, potentially provoking an attack! Normally, you only get one attack per round, so Haynuus can choose when he wants to attack the Trolin - usualyl sooner is better than later.
Note that if Haynuus possessed the correct feat, he could get additional attacks of opportunity per round.
However, even then he could only attack a character moving out of his threat range once.. However, if the Trolin used a move action to bend down and pick something up, then moved, what would happen? In this case, if he could make two, he could make one for the distraction of the Trolin getting a weapon, and another for the Trolin moving. Haynuus is not allowed, however, to make two together for the movement of the Trolin.
Now, let's say Ameena was armed. Although she can make an attack of opportunity theortically, would she get an attack of opportunity, given that the Trolin is leaving her threatened range? The answer is yes, because the attack of opportunity happens before the thing that triggers it. In this case, the Trolin's attempt to leave the space beside her is what triggers, so the Trolin is still in that square (just) as the attack happens.
Meanwhile, when would Falkor get to attack assuming he was armed? The answer is only when the Trolin moved adjacent, not when the Trolin first enters into the diagnonal threatening square. However, the attack itself will happen in that diagnoal square, jsut before the Trolin lands adjacent to Falkor.
And of course, the attack of opportunity could only be with a weapon, Falkor could not shoot off a quick spell instead.
So, that's a thoroughly covered Section on Attacks of Opportunity, looking at them with a real example!
Edit: I misunderstood something to do with moving and attacks of opportunity (to do with a feat) so re-jigged the explaination.
