Giant Beaver

Most mounts hoard their reward: the creatures that saddle up hand over their tap, and the mount grows fatter for it. This one runs the payoff backward. The counter does not stick to the beaver; it lands on whichever creature you tapped to saddle it, so the crew grows and the mount stays a flat 4/4. The trigger fires only on attack while saddled, which locks the sequencing: you pay the saddle cost as a sorcery, commit small bodies to it, then swing, and the growth arrives on a creature that is (by definition) tapped and sitting out of that combat. What you build across several turns is a slow, board-wide swell, each attack fattening a different member of the team rather than the animal doing the hauling. Vigilance matters here for a specific reason: the counter only comes when the beaver attacks, never when it blocks, so keeping it upright on defense costs you nothing while the engine runs. The tension is real and deferred. The creatures you saddle with are the ones that grow, but they are also the ones tapped down and exposed the turn they pay in, so the reward is credit against present vulnerability. It is a repeatable single-target buff that keeps asking for fresh bodies, and the image of a load-bearing rodent hauling a payload of growth forward is the sort of literal joke the mount frame keeps inviting.