Boundless Realms

Most ramp scales linearly: one land per Cultivate, two per Skyshroud Claim. This one doubles. Cast it with seven lands in play and seven more arrive, each a basic you choose, and the spell rewards exactly the board state where a green deck has already pulled ahead on mana. The seven-mana price tag is steep enough that you rarely want it as your first ramp piece, but by the time you can afford it, X has grown large enough that the payoff dwarfs anything a midrange ramp spell does. The lands enter tapped, so there is no same-turn explosion; the reward is deferred to the next turn, when you untap with a mana base that can have doubled. The shuffle clause tidies the thinned library, which matters less for raw card advantage than for the sheer count of permanents it deposits at once, a number that feeds landfall triggers and any payoff that counts lands hitting the battlefield rather than mana spent. It is a haymaker disguised as ramp: not the spell that gets a green deck going, but the one that turns a comfortable lead into an insurmountable one.