Bahamut, sometimes called “The Dragon King”, is one of the most popular summons in the Final Fantasy series. He has appeared in several installments, including his own game entitled “Bahamut Lagoon”. Bahamut is typically depicted as the strongest among storyline summons and most of the time, the player must prove that they are worthy by winning a battle against Bahamut himself, or in rare occasions, another storyline boss.
I don’t know from which of the Final Fantasy series this Bahamut is, but needless to say, their cosplay is fantastic! Thanks to Jazz for sending this in!
EDIT: Thanks to 愛子 藤原 for letting me know that this Bahamut came from Final Fantasy X!