Springleaf Drum

Mana acceleration usually demands you spend a real card to get it: a dork that can die, a rock that does nothing but tap for mana. The trick here is repurposing creatures you were already playing into a fixing engine without sacrificing their bodies. The cost is cheap but real: tapping a creature to the Drum means it cannot block or attack that turn, but a creature with no relevant tap ability and no urgent need to swing is paying with an activation it would otherwise waste. And because this is a standard mana ability with no timing strings attached, a freshly cast creature can crew the Drum the turn it lands, summoning sickness notwithstanding, since the Drum taps it rather than asking the creature to use its own abilities. You can hold mana up on an opponent's turn just as easily. The any-color clause is the other half: a one-mana rock that fixes for all five colors is rare, and tying that fixing to the creatures you control rather than to an explicit color identity has carried it across formats with wildly different mana demands. It is best understood as a bridge between the creature-count axis and the mana axis, converting a board state into colored mana on demand. Removal and sweepers blunt it by thinning the bodies it leans on, but in wide shells where one tapped creature goes unmissed, it behaves closer to free fixing than a genuine cost.