Prismatic Omen

• WWizards of the Coast2008-05-01
  Official Ruling
  Each land you control will have the land types Plains, Island, Swamp, Mountain, and Forest. They’ll also have the mana ability of each basic land type (for example, Forests can tap to produce ). They’ll still have their other subtypes and abilities.
• WWizards of the Coast2008-05-01
  Official Ruling
  Giving a land extra basic land types doesn’t change its name or whether it’s legendary or basic.

Rulings via Scryfall