While you need a bunch of creatures and noncreature spells to really take advantage of it (which probably limits it to token decks), it can be an engine that takes over the game in the right deck
By pairing Teval with cards like The Gitrog Monster or Insidious Roots, you can create an engine that keeps your graveyard active and your board full of protective tokens, making your walkers nearly impossible to reach in combat
Let the Mewtwo Wars Begin Black & WhiteNext Destinies , #54/99 (Illustrator: Shizurow) After its success in the first few expansions, Mewtwo wasnt especially effective in competitive play
The drop rates for each card slot offered by codes can be found on the official Pokmon TCG Live website
These ratios may change for future sets
That said, they can always be tapped in addition to other creatures with the appropriate crew values