Final Fantasy Resonance Guide | How to Beat the Water Shrine Boss in Chapter 3 for 10,000+ Damage in One Attack

Alluvion is the final boss of the Water Shrine in Chapter 3. The boss is weak to Thunder, but your early party may not have a strong enough Lightning spell to take advantage of it. You can solve that by defeating a Mind Flayer before returning to the shrine. Its Magicite lets you awaken Tronn and unlock Thundaga for Archwitch Fina.

Defeat the Mind Flayer Southwest of Amore

Head to the cave southwest of Amore. The recommended level is 28, but strong Earth attacks let you attempt it below that. The Mind Flayer has two additional enemies. Take them out quickly.

Earth attacks work well against the Mind Flayer. Use Witching Hour with Archwitch Fina, then Magic Boost before your strongest Earth spell. One hit can reach around 9,300 damage. Keep attacking until the Mind Flayer falls. It drops the full Magicite needed for the next step.

Awaken Tronn and Unlock Thundaga

Use the Magicite at the Moogle of Light's Vision Enhancement menu. Select Tronn and awaken it to two stars to unlock Firaga, Blizzaga, and Thundaga. This upgrade requires a full Magicite, not a Magicite Shard. 

Equip Tronn on Archwitch Fina and make sure Thundaga is available in her skill list. This is the main reason for taking the detour before entering the Water Shrine boss fight.

Prepare the Party for Alluvion

Return to the Water Shrine and travel to the final save point before the boss. Use Rain, Lasswell, Nicho,l and Archwitch Fina. Fina handles the main damage while the others provide support and stagger pressure.

Rest in a Tent to restore HP and MP. Open with Hastega and Libra to reveal Alluvion's weaknesses. Alluvion is weak to Thunder and nullifies Water, so avoid Water attacks. If you have already unlocked Ramuh, summon him during the fight for extra damage. 

Use Witching Hour, Magic Boost, and Thundaga

When the Prism Cores appear, defeat them before returning to Alluvion. They are also weak to Thunder, and the boss's special attack grows stronger when it absorbs them. Keep the party healthy and build toward the next stagger.

Activate Witching Hour on Archwitch Fina before preparing your main attack. It raises all her attributes by 50%, but blocks white-magic healing. The Chocobo Down Charm helps protect her by allowing her to survive a lethal hit with 1 HP once per battle. Watch her HP and MP; use End Witching Hour before healing her with white magic. 

Before casting, use Magic Boost on Thundaga. It doubles the selected spell's damage at the cost of 50% more MP. With Witching Hour active and Alluvion's Thunder weakness exposed, Archwitch Fina can deal more than 10,000 damage with one Thundaga. Repeat when the gauge and MP allow, while the rest of the party supports Fina.

Defeat the Mind Flayer, awaken Tronn to two stars, and use Witching Hour with Magic Boosted Thundaga to bring down Alluvion quickly.

FAQ

Q. Where do you get Thundaga before the Water Shrine?

A. Defeat the Mind Flayer in the cave southwest of Amore, take its Magicite to the Moogle of Light, and awaken Tronn to two stars.

Q. What is Alluvion weak to?

A. Alluvion is weak to Thunder and nullifies Water, so Thundaga is an effective choice.

Q. Can Archwitch Fina be healed during Witching Hour?

A. No. Witching Hour nullifies healing from white magic while active. Turn it off with End Witching Hour before healing her.