Ulamog's Dreadsire

• WOTC Official Reminder Textofficial rules
  Vigilance — Attacking doesn't cause this creature to tap.
• WOTC Official Reminder Textofficial rules
  Ward — Whenever this permanent becomes the target of a spell or ability an opponent controls, counter it unless that player pays [cost].

• WWizards of the Coast2024-06-07
  Official Ruling
  If a permanent on the battlefield has in its mana cost, X is 0 when determining its mana value.
• WWizards of the Coast2024-06-07
  Official Ruling
  The mana value of a face-down permanent is 0.
• WWizards of the Coast2024-06-07
  Official Ruling
  The mana value of a token that isn't a copy of another object is 0.

Rulings via Scryfall