Greninja EX is a neat card, nothing too great
Yes, there are builds where you can stock your graveyard up, but Im thinking you could reanimate this blue creature with something like Unearth or Helping Hand, or play it in a tempo build and cheat it in without casting with something like Collected Company
Oh hey look rules notes: A card cast for its Prototype cost has its prototype characteristics (mana cost, power and toughness) on the stack and on the battlefield
16 and 813
Even better, Vial Smasher has partner, meaning you can bring in another creature to your deck, giving you access to more colors to play a wider variety of Goblin creatures and more impactful spells
New sets drop regularly, the meta shifts, and collectors get fresh art, chase cards, and mechanics to nerd out about