Materia Needed:
Final Attack(Level 3 or higher)
Phoenix (Should be in the same level as Final Attack)
3 Mime
W-Summon
Knights of Round
Underwater Materia
HP Absorb
MP Absorb

First, give everyone a mime and pair Final Attack with Phoenix on Cloud
Give him Knights of Round paired with HP Absorb, and W-Summon
Give someone the Underwater Materia
Go to fight Emerald
First of, let Cloud use Knights of Round two times with the W-Summon. When he attacks, he will recive 9999 HP from the magic.
The next character will Mime, and so will the next. Keep on Miming untill Emerald dies. If he takes you out instead, Phoenix and Final Attack will take you back.

When you have killed Emerald Weapon, go to the Kalm Traveller and give him the Earth Harp. You will get Master Magic, Master Summon and Master Command.