Originally Posted by Me. Yes, me! Not you, but ME!
FFVI: Yes... he DO appear in this game but he's called Atma weapon. Now you may think: "WTF? Atma Weapon has NOTHING to do with Ultima Weapon!" BUT YOU'RE WRONG! Time for the Atma=Ultima theory...
In FFVI there's a creature called Atma Weapon. But his real name is... Ultima Weapon. Why do I (and others) think so?
Reasons: 1) The name "Ultima Weapon" includes more letters than it's possible to have in a monster's name in FFVI. Therefore it had to be cut down to Utma Weapon. Now, atleast 2 things could have happened. Either... they changed Utma Weapon to Atma Weapon because it sounds cooler... or maybe... the calculator replaced the U with an A just because, as we all know, the translators are weird. 2) There's a sword called Atma Weapon in FFVI... and there's a sword called Ultima Weapon in FFVII, FFVIII(the creature weilds it) and FFIX.(and in japan, Tidus best weapon is also called Ultima Weapon instead of "whatever the name of his best weapon is"). In FFVI a schoolar tells you about the Atma sword. It's a sword created by the wielder's spirit (or something like that). Now... did you notice that Ultima Weapon (the sword) changes colour when Cloud's hp is low? Because he's close to die and if he dies, his spirit leaves him. This make both Atma and Ultima Weapon get weaker when your HP is low but extremely strong when your HP is high. That's because it's the same sword! 3) The look of Atma Weapon actually reminds a little of the lower part of Ultima Weapon's body in FFVIII. 4) You can kill Atma Weapon by taking away all its MP and in FFVII Ultima(te) Weapon only have MP based attacks, which means that if you take away his MP he becomes completely unable to perform any action. 5) If you scan FFX-2s Ultima Weapon, the description of the monster says: "Whatever you do... don't call it Atma." Of course not! Because his true name never was Atma. His true name was Ultima Weapon all the time. They just had to take away 2 letters (L and I) and all that stuff.