Crested Sunmare

The token trigger asks for exactly one thing: that you gained life this turn. The engine bootstraps itself from there. The first 5/5 it makes at end step is a Horse, which means the anthem grants it indestructible the instant it enters, and every Horse after that arrives into the same protection. So the loop closes on a single input: gain a point of life each turn and the board thickens with 5/5s that damage sweepers and destruction effects simply cannot touch. What throttles the whole thing is elegant in its plainness. The lifegain condition is a per-turn meter, so a turn without lifegain is a turn without a token, and the deck around it has to keep the trickle going. The sharper restraint is the word "other." Indestructible extends to your Horses, not to the Sunmare itself, so the piece manufacturing the army is the one piece a targeted removal spell can still answer. That self-exclusion is the deliberate weakness in the design: the factory is fragile even as its output is nearly indelible. It reads as the reward at the top of a dedicated lifegain shell rather than a bomb you jam anywhere, because incidental lifegain snowballs the end-step tokens into a wall faster than most decks can race, while one well-aimed answer on the Sunmare quietly stops the line before the next token ever lands.