Primal Amulet // Primal Wellspring

A cost reducer that earns its way into becoming a copy engine, and the gating is what makes the design cohere. As a static four-mana rock it trims a generic from your instants and sorceries, unremarkable until you notice charge counters accumulating with every instant or sorcery you cast. Hit four and you flip it, and the back side stops caring about cost reduction entirely: it becomes a mana source whose mana is poison for one-shot spells, copying anything it pays for. The two faces ask for different things from the same deck. The front rewards casting cheap spells in volume, the back rewards casting one expensive spell with the copy attached, and a spells-matter deck is already shaped to do both. The transform is gated rather than automatic, which is the discipline here: you cannot flip on your own terms by feeding it counters out of nowhere; you flip by playing the game it wants you to play. The copy clause also dodges the usual fork-spell limitation of being one-shot, because the Wellspring stays in play and can tap again next turn, turning a single mana ability into a recurring spell-doubler. Most cost reducers are passive and most copy engines are fragile and expensive; folding both into one permanent that upgrades through normal play is the idea, and the four-counter threshold is what keeps the upgrade from being free.