Wow.. first time I see this thread and already it's full of very cool ideas.
I love that Boomerang idea, although it might be a bit overpowered as it looks to be the ultimate deck-out prevention tool. Very cool idea though.
I think Bloodshadow's card breaks the rule #1 and maybe #7. It generates a "Shade", a creature that does not exist in Elements, therefore basically combining two different ideas. It's unfair if one contestant can use this kind of method to get more depth into his/her idea.