Glistening Sphere

Most color-fixing artifacts pay for their reach by entering tapped, a turn of tempo the fixing is supposed to justify. This one hands part of that tempo back on the way in: an enters trigger proliferates, letting you add a counter to any players and permanents that already have one. That trigger is the design's tell. The rock lands into a board it is also advancing, so the play that stumbles into a tapped mana source can also push an opponent already carrying poison closer to the threshold it cares about. That threshold gates a second activated ability: once an opponent has three or more poison, the artifact can tap for three mana of a single color instead of one of any. The baseline any-color tap never goes away; the corrupted mode is an added option that the board state unlocks, not a replacement that switches on. That distinction is the whole strategic shape. Absent a poison plan, you own a fixing rock that arrived a turn slow and nothing more; the proliferate does nothing if no counters are in play to grow. With toxic pressure already in motion, the tripled output turns a fixing slot into a ramp burst steep enough to fund a closing turn, and the entry proliferate helps advance the very condition it wants. It is a mana source built as a payoff: it rewards a deck committed to poison, and earns its slot before that payoff comes online by fixing colors in the meantime.