Abandoned Air Temple

The enters-tapped clause is the price of admission, and it is written to reward the deck this land actually belongs in: control a basic and it comes down untapped, so a white-based build that keeps real basics in the mix pays nothing, while the nonbasic-heavy pile eats the tempo tax. That is the whole exchange for the front half. The reason this earns a slot over a plain white source is the back half: a late-game mana sink that drops a permanent +1/+1 counter on your entire board. This is the classic activated-land bargain, a card that makes mana while you develop and then converts flood into board presence once the spells run dry, without ever costing a slot a spell would have filled. Because the activation carries no timing restriction, it fires at instant speed: hold the mana, then pump in response to a fizzled wipe or mid-combat to swing a race. The counters are permanent and hit every creature, so the ability scales with a wide board rather than inflating a single attacker; it is a go-wide payoff bolted onto a color source, not a way to make one threat enormous. And at four mana plus the tap, the cost is deliberately steep enough that it never competes with the turn's real play. It only shows up when there is nothing left worth casting.