Jet Medallion

One member of the Medallion cycle, the five colorless rocks that each shave a generic mana off spells of a single color, and the one most often pointed to as the dangerous one. The discount-per-color design is deceptively flat: it saves only a single mana per spell, but it scales with how many of your colored spells you can chain in a turn, which is exactly what black ritual-and-recursion shells want. The reason this color in particular draws scrutiny is that black has the easiest time converting a generic discount into explosive turns: cheap card draw that refunds itself, tutors that find the payoff, and a long history of fast-mana effects that the discount stacks on top of rather than competing with. Unlike a true ritual, it does not generate mana, so it cannot be sacrificed for a burst; the value is purely a standing tax reduction, which means it rewards density of black spells over any single big payoff. That distinction is the design discipline holding it in check: it is a multiplier on volume, not a one-shot accelerant, so a deck has to actually be built around casting many black spells to extract the rate. Reprinted across multiple sets since its debut, it remains the canonical reference point whenever a designer wants to give a color a per-spell cost reduction and has to decide how much that color can be trusted with one.