Cuchulainn, the Impure is one of the earliest Espers that players can obtain but it’s also a difficult fight. If you’re looking to obtain everything in Final Fantasy XII: The Zodiac Age you’ll have to fight this behemoth and we have the strategy to ensure your victory.


Cuchulainn requires you to complete the “Waterway Haunting” and the “Lost in the Pudding” hunts beforehand. This will give you access to the Sulce Gate Key which is necessary for the puzzle ahead. Cuchulainn is one of the most vexing Espers to locate in Final Fantasy XII but here’s the solution:

  1. Interact with the switches so that 3 and 10 lights are on and 4 and 11 lights are off
  2. Head down Number 3 Cloaca Spur to the south west and use the control at the far end to close Number 1 South Waterway
  3. Return to the central control and swap all the switches –  4 and 11 lights on and  3 and 10 lights off.
  4. Head down Number 4 Cloaca Spur and use the control at the far end to close Number 2 South Waterway.
  5. Return to central control and operate the switches so that 3 and 4 lights on and 10 and 11 are lights off.
  6. Head directly south down Number 1 Cloaca to a large area of water where Cuchulainn waits.


Throughout the battle, you’ll be inflicted with Sap thanks to Cuchulainn’s toxin that cannot be dispelled. On top of the uncurable Sap Cuchulainn can inflict another Sap on your party, that’s double the health drainage.

Use Black Belts to counter the Disable Spell and Dispel Cuchulainn’s Haste. Assign one party member to healing and nothing else, if possible assign another member to Esunaga, Arise, and Raise to minimize MP cost.

Cuchulainn’s main means of attack are Toxify and Bio. He’ll also use Slow and Disable to keep your party away. “Invert” is terrible since it swaps your HP and MP values but avoid Cuchulainn until it wears off.

Foobars will begin to enter the battle, take them down. They’re weak to Light/Holy magic. Once all 4 have died, focus your attention on Cuchulainn. Cuchulainn will panic and start using Drain and Mana Spring to heal himself and recover MP for Bio. Once Cuchulainn falls below 15% he’ll increase defense, unleash your Quickenings and earn the Esper’s power.

Please check out our other guides for defeating every hidden Esper in Final Fantasy XII: The Zodiac Age:

How to Locate and Defeat Adrammelech, the Wroth
How to Locate and Defeat Zeromus, The Condemner
How to Locate and Defeat Exodus the Judge-Sal
How to Locate and Defeat Zalera, the Death Seriph
How to Locate and Defeat Chaos, Walker of the Wheel
How to Locate and Defeat Ultima, the High Seraph
How to Locate and Defeat Zodiark, Keeper of Precepts