Greater Sphere is an enemy in Final Fantasy X, bred as an Original Creation at the Monster Arena. It looks and attacks similar to the Spherimorph boss from Macalania Woods. Greater Sphere is unlocked after two Species Conquest monsters are bred.
The Greater Sphere is vulnerable to an element, but shifts it randomly once hit by its weakness. Unlike the Spherimorph, the Greater Sphere absorbs any other element. After the Greater Sphere attacks with an elemental attack, it will be weak to that attack's opposite element.
It will counter all normal attacks with Ultima, or Flare if healed with a Potion, Hi-Potion, or Mega-Potion for whatever reason. On its turn it will alternate between a normal attack and unleashing Hydraulic Press, which deals fractional damage to the party, equal to 15/16 of each character's maximum HP. For every Overdrive the Greater Sphere survives it will counter with Hydraulic Press. The damage from Hydraulic Press can be reduced using Protect and Defend.
It drops weapons with One MP Cost and armor with Auto-Phoenix, and a Luck Sphere. Its equipment drops provide a 6% critical hit chance bonus instead of the usual 3% (this is relevant to weapons and armor, but only to attacks that deal physical damage).
The Greater Sphere is unusually time consuming to defeat and very powerful. Auto-abilities, such as Break HP Limit, Auto-Haste, Auto-Protect, and Auto-Shell, prove helpful, and a high Magic Defense attribute is vital. Before attacking Greater Sphere, the player should be prepared to weather its Ultima counterattack.
When farming Greater Sphere for Luck Spheres, the player will want to kill it as fast as possible. The fastest strategy is to use Tidus's and Wakka's Overdrives, Slice & Dice (if successful) and Attack Reels with 12-hits respectively (both once), to defeat it quickly. Using Auto-Life will make this strategy easier.
Another helpful strategy is to summon Anima and cast Protect and Haste. If Anima loses health, she should cast Curaga. She should use Oblivion when it becomes available. If Oblivion doesn't finish Greater Sphere, Anima may suffer damage from Hydraulic Press up to three times (which might end up killing her). This strategy is only viable in the International/PAL/HD versions.