The Deep Sea Research Center is an old abandoned research center located at the bottom left of the map. You can only enter the research center with the Ragnarok.

¤ Bahamut

When inside the research center you find yourself in a room with a blue flashing core. You need to go to the core and inspect it. But it's not that easy to get there, because when you walk when the blue light flashes, you'll get a battle. So, walk when the light doesn't flash.
When you get to the core a couple of questions will be asked. Whichever answer you give, you have to fight a Ruby Dragon. But when you give the right answer you move on to the next question. Watch out that you can't heal yourself between battles.

Here are the right answers to the questions:
Q: So you wish to challenge me?
A: It's not our will to fight
Q: Begging me for mercy?
A: Never
Q: Damned imbeciles. Why do you wish to fight?
To answer this question, select the hidden option underneath "None of your business".

After your fight against Bahamut, he will join you.

¤ Ultima Weapon

Re-enter the Deep Sea Research Center again after you defeated Bahamut. You'll find a save point and a way down through a hole in the floor. Then check the machine to the right to find out there's a pressure problem. You have to make your way down six floors and you start with 20 Pressure units. If you use to much units you won't be able to get down all six floors.

• Floor 1: Use 4 units to open the door to floor 2 (16 units left)
• Floor 2: Use 2 units to open the door to floor 3 (14 units left)
• Floor 3: Use 4 units to open the steam room and then boost the count with 7 units. Then use 1 unit to open the door to floor 4 (16 units left)
• Floor 4: Use 1 units to open the door to floor 5 (15 units left)
• Floor 5: Use 1 units to activate the lift that leeds to the 6th floor (14 units left)
• Floor 6: You'll need 4 units to open the ocean deposit door (10 units left)

Note: Don't let Zell do things if he's in your party. If you let Zell handle things the random battles will be really a pain and Enc-None won't help.

With 10 units left save your game and head all the way down to the next control panel. When you have pressed the button an alarm will sound and Ultima Weapon will come out and play.

Ultima Weapon one of the thougest bosses in the game. He is fast and has some powerfull spells like Meteor, Gravija and Light Pillar (9999 HP damage). He's weak against Ice and absurbs Fire. Make sure to cast Haste, Protect and Triple and use Aura to have your Limit Break ready. Also be sure to draw Eden from him. If you forgot you can always draw it from Tiamat at Ultimecia's Castle.