Guardian Idol

Mana rocks that only make mana have always carried a hidden cost: once your curve is full, they sit there doing nothing. This one answers that by stapling the mana ability to a manland-style backup, so the dead-draw turns late convert into a clock or a blocker. The enters-tapped clause is the toll for that flexibility: you lose a turn of acceleration up front, so it never quite competes with the pure ramp pieces that come online immediately. The Golem mode is deliberately modest: a 2/2 that has to be reactivated every turn it wants to attack or block, never threatening to outshine a real creature. It exists to give the rock a floor when the game grinds out and the spare colorless mana has nowhere better to go. That two-job design (accelerate early, swing late) made it a fixture in colorless artifact builds long before "mana rock with upside" became a recognized deckbuilding category. Note that it only adds colorless, so it ramps but does nothing to fix your colors; the body is the upside, not the mana flexibility. It is the template a lot of later two-mana rocks were measured against: do you get a body, or just the mana? Here you get both, at the cost of tempo on the turn it lands.