i still like the seal of orichalcos idea but lets go about it a different way instead of making a deck based around lol the seal make a deck that must have the seal in it  that way it wouldnt be so hard of a deck to build so u can accomidate cards like grave keepers earthbound immortals u know the works

something like this ?^

too little diversity for it to be fun, by basing a tournament around one card the little variance makes it not appealing.

that still same idea. U should make something more complex

well the other idea i had was the deck master tournament if it hasnt been done already