Cumulative upkeep (At the beginning of your upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it.)
As Illusionary Terrain enters the battlefield, choose two basic land types.
Basic lands of the first chosen type are the second chosen type.

"The drawing of maps is fruitless in the west near the ice walls; the very earth is formless."
—Disa the Restless, journal entry