The Esper of Water is the fourth summon board released. It has one of the game’s best blessings. The blessing reduces the enemy’s SPD (which means more turns for your party) and grants a permanent BRV regen buff once your character’s HP falls below 80%. The Leviathan blessing is very good for units with free turns.
How to access:
You need to level up the summon to level 20 to unlock World of Illusions: Leviathan Ultimate, and then farm materials on it to reach level 30 and access the CHAOS stage.
Stage Difficulty: Level 180 (SP cost: 5)
Mission Requirements:
Score 640k |Clear without any KOs | Clear within 65 turns | Take 10000 or less HP damage
Boosted Characters: All
Event Characters: Krile, Zell, Laguna, Shantotto, Tifa, Kefka
Various team options with and without boosted characters are available in this event’s Call to Arms, and here are some examples:
| Krile Run Krile EX+3LB Relm Sherlotta | Zell Run Zell EX+3LB Selphie Sherlotta | Team Comp #1 Noctis EX+3LB Ignis EX+2LB Prompto | Team Comp #2 Yuffie Cloud EX+3LB Zack EX+3LB | Team Comp #3 Lightning EX+3LB Hope EX+0LB Vanille EX+3LB | Team Comp #4 Aranea EX+3LB Vayne EX+3LB Leo EX+3LB | |
| Turns | 38 | 61 | 62 | 53 | 43 | 38 |
| Friend | Sherlotta | Sherlotta | None | Aranea | Leo | None |
| Score | 829k | 651k | 647k | 787K | 934k | 999k |
| Summon | Ramuh | Ramuh | Ramuh | Ramuh | Ramuh | Ramuh |
| Video Link | Click Here | Click Here | Click Here | Click Here | Click Here | Click Here |
| Creator | SnoopBallPH | SlidePH | DFFOO GL SO | DFFOO GL SO | DFFOO GL SO | DFFOO GL SO |
Fight overview
At the time of its release, it was one of the hardest CHAOS as we had a limited batch of viable EX+ units.
You need to delay the Leviathan before it floods your party with its Tsunami attack. (Yes. It will use Tsunami on its first turn.) After using Tsunami, Leviathan will gain 
1T Leviathan Scales (raises DEF, SPD) and strong resistances against all elements except for 
until its next turn. To make the matters worse, the field effect Whirlpool grants Leviathan massive BRV regen while inflicting Sap on your party. Every action your party members take will add BRV to its pool.
Like Shiva and Ramuh, Leviathan also gains a Resist Veil upon breaking a character. All HP damage will be nullified until it has been inflicted with a break.
The event synergy characters have a lot of means to counter its gimmicks – inflict Thunder elemental weakness (Krile), Sap and Poison to drain its BRV regen (Kefka, Shantotto), debuffs to weaken the boss (Laguna) or launches to delay the Water dragon (Tifa). Zell is there for the high DPT to speed up the battle. The battle has a very tight turn count (65 turns for a CHAOS fight).
Wave 1: Leviathan
| BRV Attack |     attack |
| Spume | Increases BRV when BRV less than INT BRV;  attack |
| Hydroshot | attack; high turn rate |
| Gush | Recovers from Break; attack + attack; cancels MAG ATK boost from “Attacks grown more powerful!” |
| High Tide |  attack;inflicts  ATK Down |
| Tidal Spiral | attack; inflicts SPD Down;high turn rate |
Tsunami | Recast ability; increases BRV; attack;applies Whirlpool to field (grants Leviathan BRV Regen); grants 1T Leviathan Scales (raises DEF, SPD) to self;inflicts Sap;changes all resistances except to tough until Leviathan’s next turn+ version: greater BRV increase |
Gathering waters…!: Raises ATK, DEF, SPD, INT BRV, MAX BRV (activates at 80% HP)
Further gathering waters…!: Raises ATK, DEF, SPD, INT BRV, MAX BRV further (activates at 50% HP)
Resist Veil: Triggered when inflicting Break or attacking a broken target; nullifies HP damage; canceled when afflicted with Break
As the turn requirement is only 65 turns, do expect that you need to burst out as much damage as you could within the turns that you need. Units with high DPT are highly recommended.
It is recommended that you deploy someone who uses Thunder element since the boss will resist every element except Thunder after it uses Tsunami (Beatrix, Lightning, Edge and Krile are some of examples of Thunder DPT).
A dispeller can help to weaken Leviathan’s SPD and DEF. Debuffers that offer poison or sap will help against the BRV regen that Leviathan gains. Do note that the BRV gain gets larger as each turn passes. Leviathan can be silenced (Agrias’ Hallowed Bolt) and paralyzed (Cloud, Gilgamesh, Ashe (EX only), Agrias – but Kam’lanaut is not recommended since the Leviathan strongly resists Ice). If you have Yuffie with her EX, she will cheese all the mechanics that Leviathan can offer.
You can choose to delay the boss and prevent it from getting a turn for an easy clear. It is also possible to solo this CHAOS with a lot of units (Vayne, Caius, Lightning, Leo). However, those will need certain setups to clear it.
Detailed movelist breakdown
Tsunami
| Recast ability; increases BRV; attack;applies Whirlpool to field (grants Leviathan BRV Regen); grants 1T Leviathan Scales (raises DEF, SPD) to self;inflicts Sap;changes all resistances except to tough until Leviathan’s next turn+ version: greater BRV increase |
Spume
| Increases BRV when BRV less than INT BRV; attack |
Hydroshot
| attack; high turn rate |
Gush
| Recovers from Break; attack + attack; cancels MAG ATK boost from “Attacks grown more powerful!” |
Resist Veil
| Triggered when inflicting Break or attacking a broken target; nullifies HP damage; canceled when afflicted with Break. |
Tidal Spiral
| attack; inflicts SPD Down;high turn rate |
High Tide
| attack; inflicts ATK Down |