Lluwen, Imperfect Naturalist

Two hybrid mana, a 1/3 body, and a mill-four that reads like self-inflicted card disadvantage until you notice the second clause: the "then you may" lets you pull a creature or land back to the top before you draw. That is a Mulch-style dig that often gives you the crop back, folded onto a legendary druid that can be cast in mono-black or mono-green. The entry effect is only half the design, though. The activated ability turns the graveyard fuel from a byproduct into the payoff: discard a land, count the lands in your yard, and get a Worm for each one. The mill on the way in is not just card selection, it is stocking the very resource the token engine reads. That closes the loop cleanly. Every land Lluwen buries early raises the ceiling of a single late activation, and the top-of-library placement means the lands you keep are always the ones worth drawing while the ones you mill are still working for you. The tension the designers had to solve is that graveyard-matters land engines usually want to fill the yard fast but hate discarding the fixing they need to cast the enabler; the hybrid cost and the "put a land on top" line answer both, keeping the mana honest while the Worms accumulate underneath.