Yavimaya, Cradle of Growth

Urborg, Tomb of Yawgmoth did this trick for black, turning every land into a Swamp so a mono-black deck never missed a source; this is that idea handed to green, and the color context changes what it means entirely. Where the black version is chiefly fixing (Swamps make black mana, so Urborg smooths a deck's own base), a land that makes every land a Forest is a symmetrical gift and a green ramp payoff at once. Anyone playing Forest-matters cards suddenly counts every basic and dual as one: the density that Utopia Sprawl, Nissa's static engines, and any effect keying off Forests wants, delivered from a single legendary slot that costs nothing to run. It also weaponizes an old drawback. Blood Moon and Magus of the Moon turn nonbasics into Mountains and shut off fixing; land types are contested territory, and a card that blankets the board in Forests is on the other side of that same lever. The symmetry is not a flaw here, it is the point: this feeds the opponent's Forestwalk and their own type-matters cards too, which is why it reads as pure engine fuel rather than a lock piece. What it represents is green finally getting the type-flooding effect that black had carried alone for years, and getting it in the form the color actually wanted: not fixing, but a multiplier on everything that already loves seeing trees.