Using Readied Actions to Negate Opponent's Actions

If you take a readied action in response to an enemy's action, and your readied action renders him unable to complete his action (e.g. he was going to attack you and you move away, or you knock him unconscious, or some other reason) he loses the rest of any action he's already begun, per the last sentence of the 2nd paragraph of "Readying an action". Any further actions he had remaining (including the one you jumped in ahead of) can still be used, assuming he's able to do anything, either to finish his planned action or to do something else.

e.g. a charge is a full round action. If you ready an action to move when a person charges you, they move up to you, you move, and they lose the rest of their action.

A move and an attack are two actions. If an opponent moves 10 ft. to reach you, and you have readied to move when he swings at you, you then move ... but because he hasn't actually begun his swing (your movement happened before he started the swing, even though he declared it), he still has a standard action available to him. His remaining movement from his earlier move action is lost.

Can you Ready multiple actions in one turn?

You can ready only one action in a turn.

The rules state "The ready action lets you prepare to take an action later" and "You can ready a standard action, a move action, or a free action."

Both are a pretty clear implication that you can ready only one action, and all the examples and text that follows supports that implication. The fact that you can't ready a full-round action is another (if you could ready two actions that added to a full-round, why not one full-round action?).

Can you Ready a Partial Charge?

By the letter of the rules you could only ready a partial charge in a surprise round, or in other circumstances where you only have a standard action available.

That said, if you did nothing else but ready on your turn (i.e. you did not take a move action as well), I'd let you take a partial charge as your readied action. Effectively you're giving up a full round of actions to just get a standard action only.

Readying Actions and Shot on the Run

See Shot on the Run for details.

Queries About Specific Situations

Q: You can move 5ft as part of a readied action. If I ready an attack against a charging opponent, but take a five foot step diagonally forward first, I get my attack in, but does the charge attempt fail? The opponent is now in a square from which he could not normally move to when charging. Also, is the attack made against his reduced defense, or not, because he hasn't actually made his charge attack yet?

I would allow him to still attack you (after your attack) because you're in his threatened area and he completed a valid charge. I'd apply this even if the charged character moved somewhere that would not have been chargeable to begin with. Make your attack against his reduced defense for charging.

Q: What about readying a sunder attempt against a charge? Without improved sunder, does the charging guy get an AoO, despite being in the middle of a charge? What happens if his weapon snaps before he makes the charge attack? He just stands there looking like a goof, but if he had Quick Draw, could he pull another weapon and still make the charge attack?

Yes, he gets an Attack of Opportunity if you don't have Improved Sunder. If you break his weapon with your Sunder, then unless he has quick draw he can only use an unarmed attack (which may net you an Attack of Opportuniry). With Quick Draw, I'd let him produce another weapon and make his attack.

Q: What happens if on my turn I fire a missile weapon, then ready a move action to move three squares sideways when the charger reaches my threatened area. Does that mean the charge fails because the charger isn't next to me at all when the charge is executed?

He still moves, but does not get the charge attack. He may get an Attack of Opportunity if you move through his threatened area.

Q: Say I have decided to allow partial charges to be readied in my game. In this situation, does my countercharge get resolved against my opponent's reduced AC? After I've made my attack, I assume the other guy gets his charge attack against my reduced AC. It would be weird if the guy who goes first had a harder time hitting.

If you allow this, use his reduced AC. He then attacks your reduced AC.

Q: Since the change was made in IH to be able to ready actions as a Free Action, you can now take a full round action (say a full attack) and then ready an action to move 5ft (or whatever). Is this intended?

You can't ready a 5 ft step, because a 5 ft step is not a kind of action: it's a special thing you can do while doing other actions, as long as one of those other actions wasn't moving.

By the rules as written, you could of course ready a free action such as "Speak", then - as long as you hadn't moved during your action - you could take a 5 ft. step as part of your readied action.

It's a very game-y tactic though, and one I would probably house rule away if someone started using it in my games (probably by saying that while Readying itself was still a free action, the action you readied would counted as a Move Action, or its actual action type, whichever was greater.)