Shared Trauma

Most mill spells fix their cost-per-card before they resolve, sizing the effect against a single printed mana value. Join forces breaks that math by pooling the whole table's mana into the count: the controller seeds the payment, then every opponent decides whether to chip in, and the resulting pile becomes X. The wrinkle is that nobody is forced to contribute, which inverts the usual political read. A spell that threatens to deck one player draws no help; a spell where everyone wants the graveyards full draws a lot. That makes this less a mill spell than a negotiation engine, most at home in a build that wants every library thinned at once: a self-mill or graveyard-payoff plan that benefits from cards hitting bins regardless of whose they are. The single black mana up front is almost incidental; the real cost is whatever the room talks itself into paying, and the symmetry means the controller has to want the outcome for opponents as badly as for themselves. The Join forces template was built for tables where shared incentives can be manufactured, but the floor is sturdier than the politics suggest: the controller can simply pay all the mana alone, collapsing the card into a plain symmetric mill spell that mills every player for the amount paid. Even with no help, it does exactly what an X-cost mill spell would do; the table contributions are upside, not a prerequisite.