Gruul Cluestone

The whole guild-mana-rock-that-cashes-out lineage runs through this artifact and its nine guild siblings: a fixer that produces one of two colors, then folds itself into a card once the colors it makes are no longer scarce. The math is deliberately humble. Three mana to deploy, two more (in the exact pair it taps for) plus the sacrifice to replace itself, so by the time you draw the card you have spent five mana spread across multiple turns for one fixer and one cantrip. That tempo cost is the leash; a rock that fixed and cantripped for free would be a staple, and this one is priced to be a floor, not a ceiling. What it solves is the dead-late-game ramp piece: the common failure mode of mana rocks is that they rot in hand once the curve is full, and the back half of the text exists purely so the rock has somewhere to go. It is the cycle's whole pitch, structured around the idea that fixing should be temporary and convertible rather than permanent dead weight. As a design it sits in a long line of self-replacing mana sources, doing more deliberately and more slowly what cheaper rocks do for free, in exchange for the guaranteed card at the end.