ohhh shit. that would be an awesome moment in the game, that's for sure. you've just fought through the entire temple, thinking you'll get the final treasure, when suddenly BAM big baddie teleports in, gives some speech like "you think your friendship can beat my magic? i'll show you how weak it is", and BAM transforms one of your party members. cries of outrage as you unwillingly start to battle your former friend, and whenever you get a critical hit you can see the original rarity trying to break through.
Well, I imagined it would be made in segments and somewhat like the floormasters. Of course, if this was for an actual game, the style would be would be tested again and again in order to find an approach that worked. I just drew something that looked cool.