Pain Seer

• WWizards of the Coast2014-02-01
  Official Ruling
  If the mana cost of the revealed card includes , X is considered to be 0.
• WWizards of the Coast2014-02-01
  Official Ruling
  Inspired abilities don't trigger when the creature enters the battlefield.
• WWizards of the Coast2014-02-01
  Official Ruling
  If the revealed card doesn't have a mana cost (because it's a land card, for example), its mana value is 0.
• WWizards of the Coast2014-02-01
  Official Ruling
  If an inspired ability triggers during your untap step, the ability will be put on the stack at the beginning of your upkeep. If the ability creates one or more token creatures, those creatures won't be able to attack that turn (unless they gain haste).
• WWizards of the Coast2014-02-01
  Official Ruling
  Inspired abilities trigger no matter how the creature becomes untapped: by the turn-based action at the beginning of the untap step or by a spell or ability.
• WWizards of the Coast2014-02-01
  Official Ruling
  If the inspired ability includes an optional cost, you decide whether to pay that cost as the ability resolves. You can do this even if the creature leaves the battlefield in response to the ability.

Rulings via Scryfall