Well, after a few games with my Mutation deck and other Entropy decks, I discovered this:
Unupped Pandaemonium doesn't work if all opponents creatures are invulnerable (if you want to kill your own antimattered creature for example).
Normally when you PU a creature which has used the skill Dive the twin will have the doubled Attack right from the start. But if you PU a Mutation with Dive after using its skill it doesn't get the doubled value. Is it meant to be like this?