Screamer-killer will zap stuff whenever you play a big creature, which this deck likes
This Mardu deck does nothing but build out a board and attack
it lasts indefinitely, until Ambassador Blorpityblorpboop either leaves the battlefield or its base power and toughness changes again from another effect (for example, a power and toughness sticker being placed on it or its ability triggering again)
It's an investment, right
The Pikachu Star and Charizard Star cards are worth the most, each demanding high prices for a mint condition copy
The basic mono-colored ones and their new card upgrades are given to you as you complete the Color Challenges, and then you unlock the dual-colored starter decks by completing daily quests, daily/weekly wins, and leveling up