Tidalos, the Terror Wave

When Tidalos, the Terror wave deals combat
damage to a player, exile the top three cards of
defending player's library. You may cast target
instant or sorcery from among those cards
without paying their mana costs.
{6}{u}{u}: Monstrosity 8. (If this creature isn't
monstrous, put 8 +1/+1 counters on it and it becomes monstrous.)