Lorthos, the Tidemaker

• WWizards of the Coast2009-10-01
  Official Ruling
  If a targeted permanent is untapped at the time its controller's next untap step begins, this ability has no effect on it. It won't apply at some later time when the targeted permanent is tapped.
• WWizards of the Coast2009-10-01
  Official Ruling
  If an affected permanent changes controllers before its old controller's next untap step, this ability will prevent it from being untapped during its new controller's next untap step.
• WWizards of the Coast2009-10-01
  Official Ruling
  You may target any eight (or fewer) permanents. It's okay if any of them are already tapped, and it's okay if any of them are controlled by someone other than the defending player.

Rulings via Scryfall