The story will then lead to Rocket Town, where the rocket ship that had been in the town for years is being sent into space by Shinra to combat Meteor, the deadly entity threatening to destroy the world. After fighting their way onto the ship, our heroes find themselves trapped in the rocket as it takes off, with it being powered by Huge Materia. To obtain it, the player must climb up a ladder from the the cockpit, and press “Circle, Square, X, X” in order to unlock the compartment that the Huge Materia is being stored in.
After all Huge Materia is obtained, the player must take them to a particular character in Cosmo Canyon, and from his observatory the player is able to walk up to each Materia and inspect it. Three of the Huge Materia will provide rewards if the party has the necessary items. Each of the three Huge Materia is associated with a certain type of Materia, Summon, Magic and Command. If the player has, for instance, every Summon Materia, and each one is mastered, then the Huge Materia associated with Summon Materia will consume all of the mastered Summon Materia, and in exchange reward the player with a Master Summon Materia, which when equipped, gives the character access to every summon in the game, for the price of one Materia slot.
The fourth Huge Materia is simply to obtain one Summon Materia. If the player was able to get both the Bahamut and Neo Bahamut Summon Materia up until this point, then interacting with the fourth Huge Materia will reward the player with the strongest of the three summons, Bahamut Zero.