Pit Spikes: Treat spikes at the bottom of a pit as daggers, each with a +10 attack bonus. The damage bonus for each spike is +1 per 10 feet of pit depth (to a maximum of +5). Each character who falls into the pit is attacked by 1d4 spikes. This damage is in addition to any damage from the fall itself, and the statistics presented above are merely the most common variant—some traps might have far more dangerous spikes at their bottom. Pit spikes add to the average damage of the trap (see Average Damage, below).
Source: Traps
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I was wondering if there are any rules out there for more advanced pit spikes? What I have in mind is something like characters falling off the edge of some raised platform onto spikes that are 20' (or longer).
It would seem that if they don't get hit by any spikes, they'd just fall between the spikes and take falling damage when they hit the ground.
If they do hit one or more spikes, they'd take the spike damage plus they'd either get stuck in "mid-air" while impaled by one or more spikes, or slowly slide down the one or more spikes until they hit the ground.
Regardless, getting away from the trap is no easy matter. Either the character would have to cut a path in their body to extract their body from the spike, or they'd have to cut through the spike itself so they could take that section of the spike with them.
So in essence it's a kind of weird grapple that requires dealing damage to escape ... any rules (even 3PP) exist to cover this kind of thing?