Armored Ascension

• WWizards of the Coast2009-10-01
  Official Ruling
  This ability counts the number of Plains controlled by Armored Ascension’s controller, not the enchanted creature’s controller (in case they’re different players).
• WWizards of the Coast2009-10-01
  Official Ruling
  This bonus is not fixed; it changes as the number of Plains you control changes.
• WWizards of the Coast2010-08-15
  Official Ruling
  The ability cares about lands with the land type Plains, not necessarily lands named Plains.

Rulings via Scryfall