Crystalline Crawler

A mana rock that funds itself by spending its own body. The Converge counters it enters with form a battery, and the convert-a-counter-to-mana ability drains that battery one charge at a time to fix any color you need. What makes the loop more than a one-shot is the tap ability that recharges a single counter each turn: cast it for four colors of mana and you get a self-replenishing four-color fixer that reloads about as fast as it spends, so long as you only ask it for one color per turn cycle. The tension is in the trade. Every counter you cash for mana shrinks the creature, and every recharge costs you the tap, so it cannot ramp hard and attack hard in the same turn; it is a rock that occasionally remembers it has a body, or a creature that occasionally remembers it is a rock. Because Converge counts colors spent rather than total mana, the card wants to be cast as colorfully as possible: the inversion that makes it interesting is that most mana rocks reward a cheap, mono-colored caster, while this one wants its controller paying its four generic with four different colors to seed the counter pile before the first activation. In a deck with deep color requirements it becomes the rare fixer that supplies any color while slowly building toward a threat, the second mode unlocking only once the manabase no longer needs the first.