Magquaza was released without announcement on the 31st of October 2014 and is an Exclusive Pokémon.
Magquaza can be obtained by trading with other users, or by giving a Jade Orb to a Mismagius and then using the resulting Mage Orb.
Magquaza was the second unannounced release of an Exclusive Pokémon. The first place it was noticed was Eltafez's party, where the egg and Pokémon thereafter were viewable. The method through which Magquaza could be obtained was discovered soon after by a few users, and slowly began to be found by others.