Goathead, Mystery's Shroud

Goathead enters the battlefield with 5 Mystery counters on it.
Whenever you Scry or Fateseal, remove one Mystery counter from Goathead. This ability can only trigger once per turn.
{u}{g}, {t}: Look at the top 2 cards of each player's library. You may put any number of those cards on top or bottom of their owner's library. Activate this ability only if there are no Mystery counters on Goathead.