Dreadmalkin
A one-mana body that turns your dying board into its own scaling engine. The sacrifice ability is the whole design: three mana and a creature or planeswalker you were already spending buys two +1/+1 counters, so an aristocrats deck feeds it the same fodder it was going to sacrifice anyway and gets a growing menace threat as the receipt. Menace is the piece that makes the counters matter, because a 1/1 that grows into a 5/5 or larger still walks past a single blocker, and the two-blocker requirement compounds against decks that have been trading their creatures into your sacrifice fuel all game. The design leans on repetition rather than a single big turn: there is no counter cap and no once-per-turn clause, so the ceiling is whatever your board can pay for, and the floor is a body that quietly demands two blockers even before you ever activate it. What keeps it fair is the price of the fuel: every activation costs a permanent, so the card is only as strong as the death-triggers and expendable bodies surrounding it, and on its own it is a 1/1 waiting for a graveyard-and-sacrifice shell to give it a reason to exist.

