Channeler Initiate

A two-mana mana dork that arrives as a 3/4 and then mortgages that body to make colored mana. The three -1/-1 counters it demands on entry are the whole transaction: the mana ability removes a counter to add one mana of any color, so the counters have to live on the Initiate itself for it to ever produce. Self-target and you start with a stunted 0/1 that taps for any color, and each activation strips a counter, raising its power and toughness one step at a time until it climbs back to the full 3/4. That makes it a depleting battery rather than a renewable Llanowar Elves: three taps of fixing, after which the counters are gone and you keep a real creature on the board. Point the counters at something else instead and the Initiate stays a 3/4 from the start, but you have spent the mana ability entirely; with no counters on itself, it is just a beater. The design lives in that fork, and in the friction of fixing being inseparable from a creature you would rather keep big. The -1/-1 counters open a quieter line too, since they interact with anything that cares about counters being placed or removed, turning a fixing rock into a proliferation seed or a sacrifice-and-shrink enabler. It reads generous and plays conditional, the kind of mana creature where where the counters land decides what you actually bought.