This article is from the Final-Fantasy and other Square Soft Games FAQ, by firstname.lastname@example.org (Nick Zitzmann) with numerous contributions by others.
There are four Huge Materia that can be found during Disc 2 or 3:
* Huge Green Materia: Successfully win the simulated battle at
* Huge Yellow Materia: Prevent the Shinra train from crashing into
* Huge Blue Materia: Use the passcode to eject the Huge Materia
from the warhead of Cid's rocket.
* Huge Red Materia: Successfully complete the submarine attack (you
have to sink the red sub with your missiles). Then, get in your
silver sub and explore the sea floor near the chain of islands to
the south. You can then extract the Red Materia from the ruined
Huge Materia is obtained in order of location. For instance, if you
missed the Huge Materia in Cid's rocket, but you got the Huge Materia in
the submarine, the submarine Huge Materia will be the Blue Huge Materia,
and you won't receive the Red Huge Materia at all.
In order to get the Master Materia, you must have the Green, Yellow,
Blue, and Red Huge Materia. After getting them, return to Cosmo Canyon.
Bugen Hagen will let you keep the Huge Materia in his observatory. Now,
you can get the Master materia:
* To get the Master Magic materia, you must master _every_ magic
(green) materia in the game. Whether they are equipped or in
your materia list, go to Cosmo Canyon and touch the Huge Green
Materia to receive the Master Magic materia, which lets you cast
any magic spell.
* To get the Master Summon materia, you must master _every_ summon
(red) materia in the game. This means that you will have to also
have obtained Bahamut and Neo Bahamut, because the only way to get
Bahamut Zero is to take both Bahamut summon materia (mastered or
not), and touch the Huge Blue Materia. Once you've mastered all
the summon materia, go to Cosmo Canyon and touch the Huge Red
Materia to receive the Master Summon materia, which lets you call
any summoned monster.
* To get the Master Command materia, you must master these Command
(yellow) materia: Deathblow, Manipulate, Mime, Morph, Sense, Steal,
and Throw materia. Then return to Cosmo Canyon and touch the Huge
Yellow Materia to receive the Master Command materia, which has
all the abilities of the aforementioned Command materia.
You can get as many Master materia as you want, provided that you master
another whole set of materia (either buy them in stores or use the
'birth' copy) and return to Cosmo Canyon.