Rules for ending movement in an opponents space?

Question

Is there any way in Pathfinder to end your movement in another creatures space? Let's ignore the special exemptions for creatures of greatly different sizes.

The rules contain the rather absolute statement that

You can't end your movement in the same square as another creature unless it is helpless.

They further clarify that

Sometimes a character ends its movement while moving through a space where it's not allowed to stop. When that happens, put your miniature in the last legal position you occupied, or the closest legal position, if there's a legal position that's closer.

I could have sworn that in 3.5 there were rules that, if you were forced to end movement in another creatures space, you would end up prone. And I can at least imagine a scenario where the above rules break down -- tumbling through a line of several enemies and then being tripped by an AoO, for instance. There are even (contrived) scenarios where there might be no legal place to move, such as barriers being activated on readied actions.

Is there something I'm missing in the PF rules, or are they as absolute as they seem?

edit: Here's a slightly more amusing example: cast reduce person on a halfling, cast enlarge person on a human -- now they can move into the same space due to the size exemptions. Dismiss the spells. :)

However, I'm now assuming that KRyan is right here, and there simply are no rules. I looked all over the place for the "forced prone" thing I thought I remembered from 3.5, and I think it must just have been a house rule. (Although one I will continue to use, since it makes more sense to me.)

Answer 1

I believe you are incorrect; I do not think that falling prone was ever a rule. There are rules for intentionally entering the space of a creature much larger than you, but they do not involve falling prone.

And that scenario doesn’t really break down. You just go to the nearest legal space, specifically the last one you occupied unless there are others that are closer. This might wind up moving you a fair distance, perhaps, but that’s how it works. And besides, that’s a rather unlikely scenario anyway.

Answer 2

The check gets very hard if you are moving through multiple foes. You get a +5 DC for moving through a foe's space and then an additional +2 for every additional foe in your intended path. If there's a lot of people, then that is going to be a very hard check to pass. Note that this is still a single roll by the player for all the foes. That means your player fails immediately if they miss the roll. It also means that you can end their tumble at any point along their intended path you choose. You might want to pick a fail point that is somewhere near an unoccupied space.

Where this gets tricky is with opponents who have varied CMDs. If that's the case, then the player could reasonably have made it past some foes but not others. Even then, though, the foes with the higher CMDs will tend to be the front line so you still get instant failure. In the very rare case where the first few foes have a low enough CMD that the player may have passed some and then failed later opponents, you may have to adjudicate something complicated (though I'd be tempted to still rule it an insta-fail just to avoid the complications).

Some off-the-cuff guidelines for adjudication at that point (i.e. the gospel according to me):

• Make sure the tumbler had a space to get to that was legal—a plan of some kind that would have resulted in a legal movement if things hadn't gone pear-shaped. Typically, following the tumble rules for acrobatics, that should mean there's an open space not too far away (unless they have the Fast Tumble talent).
• Determine where the mishap occurred. Who had the higher CMD?
• If there's a space within about 10' of the mishap, I'd put them in that space under the justification that they failed. If things were dire and/or that space is kind of a stretch, I'd allow them another acrobatics check to see if they manage to land on their feet.
• If there is no reasonable space, then things get fun.
  • If they're there as the result of a trip, I'd let them occupy the same space as a foe but prone. If not, then I'd probably allow a reflex save to fall prone, but either way, combat modifiers are going to be thick on the ground until people space back up. Some of those modifiers will apply against the foes as things get tight.
  • If there are aggravating circumstances (like that they failed a roll badly or the foe got an excellent shot in), I might add a stunned or shaken condition.
  • If the foe has a grapple attack, or likes rolling around on the ground for some reason, I'd give the foe an automatic grapple check just for kicks.
  • If the foe has slam attacks and your player is prone in their space, I'd call them kicks for as long as the PC is on the floor.
  • I'd consider giving a standing foe with a player prone in their square a reflex save to remain on their feet due to shaky footing.

Answer 3

Pathfinder is kind of shockingly consistent about this. Even the grappling rules make it explicit that the opponents are not in the same space, and the squeezing rules make sure to mention that you can't end your turn squeezed by a creature. So, yes, the rules are absolute: No climbing on dragons, no falling prone under the bunch of kobolds you tried to tumble through.