Den Protector

The recursion engine that hides behind a 2/2. The body itself is unremarkable: a small green creature whose evasion clause only matters once it has grown. The interesting work is in how the megamorph cost reshapes the graveyard-recursion question. Most regrowth effects ask you to spend a card and a turn doing nothing but rebuying; here the rebuy is stapled to a creature you already wanted on the board, deployed face down as a placeholder and flipped at instant speed to reclaim whatever the game has cost you so far. That timing is the whole appeal: you decide which card to return only at the moment you flip, so the answer can change in response to what your opponent does, and the flip can happen on their turn. Returning any card type (a removal spell, a threat, a land, another Den Protector to start the loop again) makes it a flexible second-half engine rather than a one-shot. The +1/+1 counter from the flip is what activates the evasion, turning a defensive value play into a recurring clock that smaller blockers can't stop. It belongs to a green lineage of creatures that fold card advantage into a fair body, descending from Eternal Witness and Regrowth, but the morph shell is what separates it: it costs nothing to hold the option open, and the option resolves on your terms.