Necron Monolith

The Eternity Gate ability inverts what mill usually signifies. Filling your own graveyard is normally a cost or a liability; here the three-card dig is the resource, and the return grows the more creature-dense your library is. Each attack rebuilds an army out of the deck it burns through: every creature card among the three milled hands you a 2/2 Necron Warrior, so a swing does not just threaten damage, it manufactures the bodies that will crew the Vehicle again next combat. That circularity is the rhythm of the card. You tap creatures with total power 4 or more to move it, the attack trigger mills to make more creatures, and those creatures move it again on the following turn. The crew cost is the anchor to a real board state: the Vehicle needs creatures to attack, and the same creatures that move it get replenished by the tokens it produces. Indestructible closes off the usual answers to a large Vehicle, since neither a trading block nor targeted destruction sticks, leaving opponents to race a 7/7 flier that spawns its own blockers and attackers whenever it declares. The variance sits in the deck, not the board: load the library with lands and spells and the mill whiffs; load it with creatures and each attack compounds. It is a threat that treats its own library as ammunition and asks only that you stock it with the right kind of card.