Lair of the Hydra

The green entry in the creature-land cycle built on a single trick: a manland with no fixed body, priced by however much mana you can spare. Where earlier creature-lands committed to a set size (a 3/1, a 2/2 with evasion, a 4/4 that could not attack the turn it activated), this one scales. The X in the activation cost is the whole design, letting the land sit as an early-game mana source and then, in a long game where lands stop being useful, dump surplus mana into a Hydra as large as the board allows. What keeps that flexibility from being free is the tapped-land clause: control two or more other lands and it enters tapped, so the manabase buys the option in tempo rather than in a fixed rate. That the creature remains a land matters for how it survives: sweepers aimed at creatures catch it only while it is animated, so you can hold the activation until you mean to attack and leave it a plain land the rest of the time. Because it reverts to a noncreature land on your opponent's turn, sorcery-speed removal has no window to catch it as a creature, and it sidesteps the mass creature-hate that never touches lands. It answers the same problem every manland answers, turning a flooded draw into a threat, but it is the version that refuses to name its own ceiling.