I read the rules and compared Chris's cards to the ones from the actual game's core set. He just copied all the rules and abilities from the original cards for his homemade ones, so none of them are overpowered or useless the way his Pokemon and Yugioh cards were. In fact, there's really no way for him to break the game in his favor, since the rules don't really work like that. The best he can do is put "this power cannot be copied" on nearly all of his cards, which is a relatively rare ability in the original game.