Terraformer

Mass land-type assignment as a repeatable creature ability is a corner of the design space almost nobody else occupies, and the wrinkle worth chasing is not the color fixing (which it does) but how it interacts with cards that read the type line rather than the color of your lands. Pay a single mana and every land you control answers to one basic type until end of turn, which switches on your own type-matters payoffs: effects that reward controlling a Mountain or an Island, abilities that count types you own, anything keyed to what your lands are rather than what your opponent's are. The scope is the constraint that defines it: the ability touches only lands you control, so it cannot retype an opponent's board. That rules out a whole class of targets, landwalk chief among them, since landwalk checks the defending player's lands; painting your own permanents the same type does nothing for an attacker swinging through. The distinction from a sorcery that performs the same swap once is that this one returns every turn, redrawing the type line as the board changes for the same cheap activation. The 2/2 is just a delivery chassis for the ability. None of this matters in a deck that wants its lands to behave like lands; it rewrites the arithmetic only in a shell built around what your own land types are doing.