Diamond Valley is a little-mentioned member of the Reserved List, with just one printing back in 1993, and both its age and its obscurity make sales infrequent
Since modern EDH has many decks that deploy creatures at any power level, you need enough support to ensure you don't end up in a situation where you can't attack anywhere, and to avoid trading creatures
The payoff for all this work is that at the beginning of your turn, you draw cards and gain life equal to the number of permanents you own but other players control
Bodybuilding Dumbbells does make it difficult for Pokmon like Giratina to Knock Out
The book shrieks horribly until its cover is opened, granting the spirit inside a moments rest from the painful stirrings of the books contents
Still, its Giovanni and Mewtwo, and thats enough for most to smash open their piggybanks