Ok,
I am fairly sure this has been asked before, and I seem to remember either official rules coming out, or someone coming up with some really neat house rules for it, but, my google fu has failed me.
Assuming you have an opponent who is at least 1 (or 2 if want), sizes larger than you, how do you rule this in your games? We have some epic monsters in Pathfinder, which are begging for those with the skills and lack of a sense of mortality to attempt to parkour off of...
Any ideas are welcome... Thanks...
~Elvnsword~
There's no official rule that I know of that allows it specifically. The best bet if something like that does exist would be in the Giant Hunter's Handbook, but I haven't had a chance to read the whole thing. There are some examples, like the Kaiju's 'Massive' trait, that come close but not quite, and are limited to very specific situations.
In my games I would allow it, although it would be pretty difficult. It would go something like:
-Acrobatics or Climb check to get up to the right height; using the normal rules if they are climbing a wall nearby, or jumping from a ledge or straight up, likely provoking an AoO due to moving around within the opponent's threat range. If they want to climb the opponent itself to get there, it would provoke an additional AoO and have a Climb or maybe Grapple check with a DC of 10 + the opponent's CMD
-Acrobatics check to stay standing once up there, with a normal DC of 10 + the opponent's CMD each round
-If the opponent moves or attacks someone else or such, DC 15 + opponent's CMD to stay on
-If the parkour-er attacks or does anything other than just focus on maintaining balance, DC 15 + opponent's CMD to stay on, and probably provokes an AoO
-If the opponent attacks the parkour-er or takes a move action to shake them off, DC 20 + opponent's CMD to stay on
-DC 10 + damage taken + opponent's CMD if the parkour-er is hit by anything.
That might honestly still be too easy for such a maneuver, maybe another +5 to the DCs across the board would be better. I would have to test it more.
The parkour-er would not share the space with the opponent, but instead be in the space above. It would also be best to have a size limitation; the parkour-er needing to be two sizes smaller than the opponent would probably be good (just one size different doesn't seem quite enough in most cases, although depending on which specific creatures are involved I might allow it).
For the opponent's CMD in this specific case I would invert the size bonus (Huge creatures would get -2 instead of +2 for example), as bigger creatures are more likely to be easier to stand on and might have a harder time throwing someone off.
All houserules of course, and mainly because as a GM I tend to be more lenient for the 'Rule of Cool'. There are plenty of people that are against the idea of anything close to such a maneuver, so even if you are the GM and its a home game, best to discuss with your whole group and make sure they are okay with it first.