When does a runner regain his Dexterity bonus to AC?

Question

The combat action run says

You can run as a full-round action. (If you do, you do not also get a 5-foot step.) When you run, you can move up to four times your speed in a straight line (or three times your speed if you’re in heavy armor). You lose any Dexterity bonus to AC unless you have the Run feat. (Player's Handbook 144)

(Links mine.) Unlike the special attack charge that specifically says that a creature that charges suffers "a −2 penalty to [its] AC until the start of [its] next turn" (PH 155), a creature that takes the action run seems to be lose its Dexterity bonus to Armor Class only while running on its own turn, regaining its Dexterity bonus to Armor Class upon its turn ending—that is, when it stops running.

However, my players were shocked during a recent session when the advanced mama phargion (Miniatures Handbook 66) took the action run on her turn and I said that on their turns—after mama phargion had taken her turn but before mama phargion had taken her next turn—that mama phargion was not losing her Dexterity bonus to Armor Class against the PCs' attacks.

My players said that their PCs should be making their attacks against a mama phargion that had lost her Dexterity bonus to AC because she ran on her turn and she hasn't yet started her next turn. I said for that to be the case, either the action run must have an exception like the special attack charge or the action run must take not a full-round action to perform but, instead, a 1-round action to perform (like casting a spell with a 1-round casting time). (This latter option would also mean the runner wouldn't reach its destination until right before its next turn—as if combat weren't complicated enough already!)

Did I rule correctly? Does a creature that takes the action run only lose its Dexterity bonus to Armor Class during its own turn, or does a creature that takes the action run lose its Dexterity bonus to Armor Class until the start of its next turn? Or is there even more to this than I realize?

Answer 1

You ruled correctly: when using the Run action, a creature loses their Dex bonus to AC only during their turn. The Charge action, Power Attack feat, Combat Expertise feat, Cleave feat, and other similar effects all explicitly state "... until the beginning of your next turn." The fact that Run does not indicates that the penalty does not continue past the action that granted it.

There was another, similar question that was posted last year and the top-rated answer came to the same conclusion.

There also seems to be some confusion as to just how long a "full-round action" takes to complete. Looking under "Cast a Spell" type of full round action shows the following:

A spell that takes 1 round to cast is a full-round action. It comes into effect just before the beginning of your turn in the round after you began casting the spell.

...

Sorcerers and bards must take more time to cast a metamagic spell (one enhanced by a metamagic feat) than a regular spell. If a spell’s normal casting time is 1 standard action, casting a metamagic version of the spell is a full-round action for a sorcerer or bard. Note that this isn’t the same as a spell with a 1-round casting time—the spell takes effect in the same round that you begin casting. [Emphasis added]

This illustrates that full-round actions, such as the Run action, happen only during your turn. This means that a running creature only loses their Dex bonus to AC during their turn since the action doesn't extend past that.

Answer 2

The rule for running reads to me that the creature or player initiating the run action would lose their dexterity modifier for THEIR turn. That being said it does not leave the players without any options for attacking the creature flat footed.

I would rule that, in the future, an intuitive player may take the opportunity of a severely hurt creature or NPC to put themselves in line for an attack of opportunity, or ready an attack against the creature if they "see them make a run for it". If there were any melee characters in range of the creature when it ran they should have clearly made an AOO against it at its flat footed AC as it left the threatened space adjacent to the attacking character.

If someone asked "Well how do I know its hurt if it's HP is out of game knowledge?", valid, until you reference knowledge skills such as Nature, Planar, Dungeoneering, Etc. (Which are completely underused in past experience) to fill the gap. Any player can make a check at the start of battle (set a DC) and be able to glean information about the creature each turn if they choose to. It also falls on the DM to use trigger statements during combat "The creature takes your blow with recoil and labored breath, it is clear this fight will not last much longer." (a little on the nose but you get the point).

My thoughts anyway. I believe you ruled correctly and it should be a lesson in placement and planning on the parties part from here on it to prevent run-aways.

Answer 3

This seems to be a problem among a few of the forums, don't think "Full-Round Action" is defined very explicitly in RAW.

A full-round action requires an entire round to complete.

In my personal interpretation, a Full-Round Action is something that is ongoing until the beginning of the next turn (hence taking an entire round to complete, not just mama's turn). A full attack action lasts six seconds in-game, but is resolved at the end of the turn IRL.

Personally, I would rule that mama phargion would be flat-footed until her next turn came around, due to that her spending a full-round action running would mean that she's running until the start of her next turn.