The Soul Stone

For most of a game, this reads as a two-mana black source and nothing else: tap it the turn it lands and it works like any other rock. The gambit is what it graduates into. Harnessing costs seven mana plus the stone's tap and the exile of a creature you control, a one-time tax that thins your own board before any payoff arrives. That exile clause is the discipline the whole thing leans on. The reward, an every-upkeep reanimation from your graveyard, would be broken as a free repeatable effect, so it is gated behind a steep activation that front-loads every cost before the value spigot opens. Indestructibility does quiet but real work: once harnessed, the recursion lives on a permanent that shrugs off sweepers and targeted destruction, so the loop is durable by construction rather than fragile. The result is a mana source that becomes a slow, grinding value engine, where paying seven-plus and a body up front is a price you can afford to eat because the returns compound turn over turn. What keeps it honest is sequencing: it accelerates you early, demands real investment to switch on, and only then begins hauling creatures back one at a time, upkeep by upkeep, rather than flooding the board all at once. The floor is a mana dork on a stick; the ceiling is a reanimation engine no wrath can touch.