Unholy Grotto

The recursion engine that costs almost nothing to run: the colorless tap pays for itself the way any utility land does, and a single black turns the second ability into a repeatable graveyard-to-library tutor for the undead. The design tension lives in the word "top." This does not return a Zombie to hand the way most recursion does; it stacks the creature on your library, so cashing in costs you a draw step. That delay is what keeps an otherwise free loop in check, and it dictates the card's strategic axis: it grinds rather than combos, refilling a board across many turns instead of assembling something explosive on one. Restricting the targets to a single tribe is what gave it a permanent home in dedicated undead shells, where re-buying a value body each turn outlasts opponents who simply run out of threats. The colorless production is the price the slot pays: it provides no colored sources of its own, so the manabase eats the opportunity cost of a Swamp in exchange for an effect that recurs forever. The result is a land doing double duty without ever feeling free, the loop metered by a clock that is always visible at the top of your library.