Nettle Sentinel

A 2/2 for a single green mana is a generous body, and the design collects the bill on the back end: it never untaps on its own, so that rate holds only as long as you keep casting green. The trigger is the engine. Every green spell you put on the stack offers to stand the creature back up, which turns a deck stuffed with cheap green cards into an attacker that comes back turn after turn while staying available to feed anything that cares about tapping and untapping. The loop rewards itself and only bites when you stop casting, which an aggressive green shell rarely does. Notice the precise wiring: the trigger fires when you cast, before the spell resolves, and it does not care whether the spell resolves or where you cast it from. It asks only that the spell be green and that it reach the stack. That timing makes it more than a beater; a chain of cheap green spells in one turn can untap it several times over. The restriction is structural rather than conditional: no death cost, no exile, no counter, just a standing demand that you keep your green count high. Build around it and the drawback evaporates; build something that wants to sit back and durdle, and the Sentinel stays tapped, a reminder that the cheap body was never actually free.