Pack Rat

A self-replicating threat that grows by consuming the same resource it asks you to spend. The activated ability builds the engine and pays its own cost in one motion: every discard makes another copy, and because each Rat counts toward the whole, every copy raises the power and toughness of all of them at once. Two Rats on the board is a pair of 2/2s; four is a wall of 4/4s, and the math compounds the longer it runs. A single removal spell shrinks the army by one but does not break the cascade: you simply activate again, provided you still have a card to feed it. That hand cost is the brake. The ability cannot fire from an empty hand, so the engine is bounded by the cards you are willing to bury, which turns the question into one of tempo: how many of your remaining resources are you prepared to convert directly into a clock, and how fast. Where most card-advantage engines spend a turn doing nothing in exchange for later value, this one inverts the trade, pouring your hand into the graveyard to widen a board the opponent must answer many times over. The design tension it resolves is the old problem of how to make discarding feel like power rather than loss. Here the discard pile is the fuel line, and the more you feed it, the harder the board becomes to unwind.