It doesn't matter if they were creatures when they entered or who controlled them when they entered
It's great for handling low Willpower evasive characters or even chipping away at Bodyguard characters
You should end up with 48 cards in total
This has some cool implications, the biggest being that while you're encountering a different Cid in every Final Fantasy game, you're always encountering the same Gilgamesh, just traveling across dimensions, looking for cool swords, and occasionally being voiced by John DiMaggio (FFXII)
Minfilia, the player's ally and Oracle of Light, sacrificed herself to halt the Flood during Heavensward
But remember, this is a support job as well, and it takes two to tango