Ugin, the Ineffable

• WWizards of the Coast2019-05-03
  Official Ruling
  Once you look at the exiled face-down card once, you may look at it again any time you wish. If another player gains control of the Spirit token, that player can't look at the exiled card.
• WWizards of the Coast2019-05-03
  Official Ruling
  A land normally has no color, even if it can produce one or more colors of mana.
• WWizards of the Coast2019-05-03
  Official Ruling
  To determine the total cost of a spell, start with the mana cost or alternative cost you're paying, add any cost increases, then apply any cost reductions (such as that of Ugin). The mana value of the spell remains unchanged, no matter what the total cost to cast it was.
• WWizards of the Coast2019-05-03
  Official Ruling
  If the Spirit leaves the battlefield for any reason, you'll put the exiled card into your hand, even if Ugin left the battlefield before that happened.
• WWizards of the Coast2019-05-03
  Official Ruling
  If an effect such as that of Doubling Season causes Ugin to create two Spirit tokens, you still only exile one card from your library. You'll put that card into your hand the first time that either of the tokens leaves the battlefield.
• WWizards of the Coast2019-05-03
  Official Ruling
  A colorless spell whose mana cost is or will cost to cast.
• WWizards of the Coast2019-05-03
  Official Ruling
  If you've activated Ugin's ability multiple times, you must keep track of which exiled card belongs to each Spirit token.

Rulings via Scryfall