Adamantoise can be found in the final dungeon . And we’d actually recommend that you simply capture one Adamantoise to add it into the Monster Arena, then you can farm(bribe) it repeatedly in there to make your life easier.
What Are Special Spheres?
Special Spheres let you activate any special ability learned by another character on the sphere grid. But let’s describe those first. Special Abilities in Final Fantasy X are actions that all have various non-damage dealing effects. Good examples include Flee and Bribe. Special Spheres are a unique item that allows any one character to learn any Special ability that’s already learned by another character, all without movement on the Grid. For example, let’s say Rikku has already learned Bribe. Wakka sees this and wants to learn it as well, but he’s all the way across the Sphere Grid. Normally you’d have to spend levels and time to get him there, but using a Special Sphere allows Wakka to instantly learn Bribe without going anywhere. Pretty handy, right? And you can also customize Defense +10% onto a piece of armor using just x1 Special Sphere. This may not be the absolute best ability you can add onto your armor, but if you want it then go for it.
Are Special Spheres Worth Farming?
Honestly, no. It’s awfully expensive to bribe just for six spheres (it’ll cost over one million gil each time). And you’ll have to wait until you’re at the end of the game to farm these anyway – so by that point there are a ton of better options for sphere grid grinding. It’s really better to just take the few given to you through chests and use them up, rather than farming for more. Special Spheres are cool, but only worth it if you really need something right now, which doesn’t happen too often.