Sanctum of Tranquil Light

The white member of the Shrine cycle turns a rate nobody would pay into one you fire every turn, but the arithmetic has a floor. Tapping a creature for is a laughable price in isolation; the ability sheds for each Shrine you control, so a wide Shrine board grinds it down to a single white mana and holds it there. Generic reductions never touch colored pips, so the effect always costs at least : not free, but close enough that the last mana of your turn buys a repeatable tapper and leaves the rest intact. That compounding reward is the entire premise of the family, each Shrine feeble alone and heavy in aggregate, and this one hands white a control lever rather than a clock. Tapping is the gentlest of the effects the cycle divides along the color pie (the black Shrines drain, the red one pings, the green one ramps, the blue one refills your hand); it suits white's assignment, since holding down an attacker or freezing a blocker is a defensive tempo tool, not a threat. Once the discount lands it functions as a pseudo-Icy Manipulator you can activate each turn for a pittance, which is exactly the payoff the ramp toward it is meant to reach. It contributes nothing early and wants a critical mass of Shrines on the board before it earns its slot, the same bargain every member of the cycle makes.