Grolnok, the Omnivore

Mill in green-blue is usually a liability you route around: cards go to the graveyard and stay there. This turns the direction of that flow into an engine. Every permanent milled off the top does not rot in the yard; it lands in exile under a croak counter, and those counters convert exile into a second, ever-growing hand that only you can play from. The design tension is deliberate: the trigger fills exile three cards at a time, but only permanents get the counter, so instants and sorceries are pure fuel that never come back. That asymmetry pushes deckbuilding toward permanent-heavy piles where the mill reads closer to card advantage than self-destruction. The croak counter is doing structural work that impulse-draw effects usually attach a clock to: here there is no clock at all, so exiled permanents wait indefinitely until you have the mana to deploy them. What emerges is a graveyard payoff that never touches the graveyard, harvesting from exile instead. The catch, and the part that shapes the whole deck, is that the mill only fires when a Frog you control attacks. The Frog typing is not flavor set-dressing; it is the ignition. To keep the exile pile filling, you need bodies with the right creature type swinging in, which ties the value engine to a tribal-aggro axis and gives the modest 3/3 a job beyond just enabling itself: it has to be a Frog, and it has to attack.