Pathfinder generally doesn't support rules for aiming hits. There are some optional rules in Ultimate Combat about "Called Shots" where you can specifically aim at certain places on the body, like the eyes or arms. See this link. It's an optional set of rules, not a part of the core rules, so it'd be something that you'd probably have to run by your GM if they'd allow.
There's nothing in there that would really lop off their arms, but would render them weak or useless.
There are no official rules for this. You could probably search for and find optional rules to cover it if you look hard enough. Simply declaring a sunder attempt on a limb would be extremely unbalanced.
Edit: Harley Quinn's right, the called shots in ultimate combat are about as close to official as you'll find.
If you're willing to use 3PP material, however, the book Strategists & Tacticians by Ryan Costello, Jr. has "severing" as a combat maneuver with feats and a prestige class dedicated to it.
Might have to house-rule it.
How about using the same rules as breaking an inanimate object? Use the leather/hide entry on the table -- the limb has Hardness 2, and 5 hit points per inch of thickness. You gotta hit, first, which is where armor class would come in.
Alternatively, you could just use the called shots method, but say that doing damage that exceeds the target's natural CON score is enough to cut off the limb.
Note that there needs to be a substantial penalty to hit, or otherwise striking to dismember would become a standard combat tactic -- made even worse when the DM starts using it as a standard tactic against the PCs. You can end up with some really messy situations if it is easier to dismember a foe than to kill him outright.
Note that there needs to be a substantial penalty to hit, or otherwise striking to dismember would become a standard combat tactic -- made even worse when the DM starts using it as a standard tactic against the PCs. You can end up with some really messy situations if it is easier to dismember a foe than to kill him outright.
Exactly, if you start (ab)using this, then the GM will eventually too, and thats where it starts getting nasty.
You dismember a nameless NPC mook, big deal, fight over, NPC forgotten and never seen again. Nameless NPC mook dismembers you, ouch, you're useless till someone casts regenerate on you. Next fight someone does it again.Worse, someone dismembers both arms of the cleric, so he can't do the somatic component of regenerate anymore, now you're completely screwed :)
It's true. Striking a balance with things like this is particularly hard in the d20 system. It's really easy to make it either too easy/powerful, or too hard/nerfed. I think this is why a good called shot system has never really been worked out and fully integrated into the rules. It's just too hard to balance!
However, since it's a feasible tactic in melee combat, there should be some way.
Hey, have you looked at the rules for the hydra? I seem to recall something specific in that monster's description about cutting off its heads. Maybe that mechanic could be borrowed in some way.