Pokemon Go has officially announced plans for a final Legendary Bird day in early September as a reward for completing this weekend's Global Challenge. The popular mobile game will host its third and final Global Challenge, in which players will need to complete over 15 million Field Research quests in order to unlock various rewards. If all the Global Challenges are successfully completed, Pokemon Go players will also unlock a special Moltres Day event on September 8th. Plus, Moltres will know the Flying-Type move Sky Attack, which it doesn't usually learn in the game.