Sorry if you guys think this is hacking. I'm not using this to abuse the game, only figure out how it works. I can allow that here (as I always have).
I've been doing some *cough*work*cough* on trying to figure this out. I changed snails to have P1 elemAttr and attacking a snail caused me to d/c on GMS. Figuring this resistance simply wasn't implemented, I decided to move to MSEA where it was implemented. I, again, changed snails to have P1 elemAttr. When I went into MSEA, I did not d/c when I hit the snails. However, I did not notice any decrease in damage. Figuring that there is no such thing as "P1", I changed the property to P2.
When I finally got around to snails again on MSEA. Here's what happened:
So... what the hell is P-resist? It's not physical, that's for damn sure.