Tainted Aether

Every creature that touches the battlefield, regardless of who put it there, demands a toll: its controller sacrifices a creature or a land of their choosing the moment it arrives. Note the narrow tax base. Artifacts, enchantments, and planeswalkers are all safe; only bodies and lands feed the clause, which is what keeps this from being a true catch-all soft lock. The effect is perfectly even-handed, so the deck running it must engineer the imbalance itself, either by deploying no creatures of its own or by leaning on permanents it can afford to bleed while the opponent's go-wide plan loses a body per arrival. It bites hardest against token swarms, where each generated creature fires the trigger and forces a grim choice between abandoning the new arrival or burning a land to keep it. Because the entering creature's controller picks the sacrifice, it never plucks a specific threat off the table; it takes whatever is cheapest to surrender, which makes it a slow grind rather than an answer, a standing penalty on board development instead of a one-shot edict. Black has rarely committed this particular idea to a continuous enchantment: taxing the act of putting creatures onto the battlefield permanently, rather than firing a single mass-sacrifice spell, remains a thin lineage. This is a lock piece for the rare deck built to win without ever needing the resource it punishes.