Instructions
Select "Auto-Battle" at the start of the fight to cast a series of offensive spells under the "Slash and Burn" paradigm. Repeat the Auto-Battle command the second time when your ATB charges.
Press "L1" to go to the Paradigm Shift menu. Select "Stumbling Block."
Select "Auto-Battle" each time your ATB fills to cast a series of debuff spells. Continue to do this until either Vanille's or Fang's hit-points are low.
Press "L1" to go into Paradigm Shift and select "Lifeguard." Use "Auto-Battle" immediately until both Vanille and Fang are completely healed.
Press "L1" again and switch back to the paradigm "Stumbling Block." Use "Auto-Battle" as frequently as possible to quickly increase Hecatoncheir's Gestalt bar with debuff spells. Switch back to "Lifeguard" whenever necessary to heal both Vanille and Fang.
Press "L1" and select "Slash and Burn" when Hecatoncheir's Gestalt gauge is near full. Select "Auto-Battle" each time your ATB fills until the Gestalt bar is full.
Press "Square" on the PlayStation 3 or "X" on the Xbox 360 to defeat Vanille's Eidolon.