Wall of text ahead

This one's been ready for a while, but I finished writing it for JP a couple months ago and ended up not posting. Updated it for the global skill names.

The main block of skill data will be removed for your sanity, with just notes on what happens with each skill during the AI sections.

There are plenty of guides available at this point, but some people might be interested in the exact data

Phase 1 - Owen

Stats and Resistances

Actions per turn: 3~4
HP: 5500000 ATK: 3500 DEF: 2000

Status Resistances:

• 50% Resistant to Injury (prevents 1750 damage per attack)
• Immune to all other ailments
  

Crit Resistance:

• Base Crit Rate is 10% (no change)
• Value of all increases to crit are halved (50% multiplier)
• Base crit damage bonus is reduced by 10% (crits deal 145-154% damage)
• Crit damage cannot be increased by any method

Elemental Weakness Damage Resistance:

• Base elemental weakness damage is reduced to 40%
• Immune to Elemental Weakness Damage bonuses

Spark Resistance:

• Base spark damage is 37.5%
• All spark damage bonuses are halved (50% multiplier)

BC/HC Resistance:

• None

Other Passives:

• 0-130% ATK bonus scaled based on amount of HP lost
  • Up to 4550 or 4680 bonus damage depending on attack used

AI Summary

• Using any items before passing 80% HP will trigger an AoE Buff Wipe DoT
  • AoE deals ~5400 damage before DEF
  • DoT deals ~4250 damage before DEF, not affected by anything else.
• 80% HP Threshold:
  • Summons Duran
  • ST BB Buff Wipe on 2 highest HP units
    • ~4300 damage before DEF
• 50% HP Threshold
  • Summons Lilith
• 40% HP Threshold:
  • ST BB Buff Wipe on 2 random units
    • ~4300 damage before DEF
• 30% HP Threshold:
  • Summons Reviora
• 15% HP Threshold
  • AoE BB Buff Wipe on all units
    • ~4300 damage before DEF
  • Only attack on this turn
• 4 turn timer: AoE Group ATK buff
  • ~6300 damage before DEF
  • Prevented by any threshold
• 25% chance per turn of a single AoE Group Crit buff
  • ~4500 damage before DEF
  • Cannot be prevented
• Normal attack priorities:
  • 15% chance of targeting earth units
  • 20% chance of targeting units over 50% HP
  • Else, random

Phase 1 - Duran

Stats and Resistances

Actions per turn: 2~3
HP: 1700000 ATK: 6000 DEF: 4000

Status Resistances:

• 70% Resistant to Injury (prevents 3000 damage per attack)
• 80% Resistant to Poison (deals 170000 damage per turn)
• Immune to all other ailments
  

Crit Resistance:

• Base Crit Rate is 9%
• Value of all increases to crit are halved (50% multiplier)
• Crit damage bonuses are reduced by 80% (multiplier)

Elemental Weakness Damage Resistance:

• Elemental Weakness Damage bonuses are reduced by 80% (20% multiplier)

Spark Resistance:

• None

BC/HC Resistance:

• 10% decrease to base BC and HC drop rate (reduced to 31.5% and 9% respectively)
• 20% multiplier penalty to all BC/HC drop rate boosts

Other Passives:

• None

AI Summary

• 40% HP Threshold: SBB (AoE chance of 50% ATK down 20% ATK down infliction buff)
  • ~7.9k damage before DEF
• Owen passes 50% HP: Overdrive -> No BB on next turn -> UBB
  • OD gives ATK/DEF self-buffs, but during Overdrive Duran can be cursed and paralysed
  • UBB: AoE (~11.6k damage before DEF) 60% ATK/DEF for 3 turns
  • If he's unable to use UBB on the turn it's supposed to activate, he'll use a BB on his next turn instead of ever using UBB
• SBB on a 3 turn timer unless Overdrive is active or activates
• BB on a 2 turn timer unless Overdrive is active or activates, or SBB activates
  • BB fires on turn immediately after UBB regardless of timers
  • BB is an AoE which can cause 50% ATK down
    • ~6.7k damage before DEF
• Normal attack priority:
  • 20%: Units with Attack type BB
  • 25%: Units over 50% HP
  • Else, random

Phase 1 - Lilith

Stats and Resistances

Actions per turn: 3
HP: 1800000 ATK: 7500 DEF: 2500

Status Resistances:

• 50% Resistant to Injury (prevents 3750 damage per attack)
• 50% Resistant to Curse
• 50% Resistant to Paralysis
• Immune to all other ailments
  

Crit Resistance:

• Base Crit Rate is 9%
• Value of all increases to crit are halved (50% multiplier)
• Crit damage bonuses are reduced by 80% (20% multiplier)

Elemental Weakness Damage Resistance:

• Elemental Weakness Damage bonuses reduced by 80% (20% multiplier)

Spark Resistance:

• Base spark damage is 37.5%
• All spark damage bonuses are halved (50% multiplier)

BC/HC Resistance:

• 10% decrease to base BC and HC drop rate (reduced to 31.5% and 9% respectively)
• 20% multiplier penalty to all BC/HC drop rate boosts

Other Passives:

• 10% chance of not being affected by Ignore DEF

AI Summary

• 90% HP: SBB (plain ST BB)
  • ~13.7k damage (unbuffed) before DEF
• 80% HP: SBB
• 70% HP: SBB
• 60% HP: SBB
• 50% HP: SBB
• Owen passes 30% HP: Overdrive -> No BB next turn -> UBB
  • OD increases ATK/DEF and makes self vulnerable to paralysis for 3 turns
  • UBB is a massive AoE that deals almost double damage to the main target and grants Owen's squad ATK/DEF buffs for 3 turns
    • ~22.5k damage AoE, 15k damage ST
  • If prevented via Curse/Paralysis, she won't use it at all
• 5 turn timer: BB (Plain ST BB stackable ATK/DEF self-buffs)
  • ~13.7k damage before DEF
  • Prevented by 90-60% thresholds and Overdrive sequence
  • Not prevented by 50% threshold
  • One additional usage after UBB
• Normal attack priority:
  • Support BB units: 20%
  • Units over 50% BB gauge: 25%
  • Else, random

Phase 1 - Reviora

Stats and Resistances

Actions per turn: 2
HP: 1900000 ATK: 7000 DEF: 6000

Status Resistances:

• 50% Resistant to Injury (prevents 3500 damage per attack)
• 10% Resistant to Sickness
• 10% Resistant to Weaken
• Immune to all other ailments
  

Crit Resistance:

• Base Crit Rate is 7.5%
• Value of all increases to crit are halved (50% multiplier)
• Base crit damage bonus is reduced by 10% (crits deal 145-154% damage)
• Crit damage cannot be increased by any method

Elemental Weakness Damage Resistance:

• Immune to elemental weakness damage bonuses

Spark Resistance:

• None

BC/HC Resistance:

• Base BC drop rate reduced to 28%
• Base HC drop rate reduced to 7%
• Value of BC/HC drop rate boosts is halved (50% multiplier)

Other Passives:

• 30% ATK boost when below 30% HP
  • Increases base damage by 2100-2130

AI Summary

• 6 turn timer: SBB (plain AoE)
  • ~12.8k damage
  • Skipped during Overdrive sequence
• 3 turn timer: BB (plain AoE)
  • ~9.2k damage
  • Skipped during Overdrive sequence and on SBB turns
• After Owen passes 15% HP: Overdrive -> Wait 2 turns -> UBB -> BB
  • Overdrive increases own ATK/DEF, makes self vulnerable to Curse/Paralysis
  • UBB is a massive AoE with BB mod buff for squad
    • ~23.4k damage
  • Can cause Paralysis or Curse during sequence; if this cancels UBB, Reviora will not attempt to use it again
• Normal attack priority:
  • 20% chance: Highest ATK
  • 25% chance: Lowest DEF
  • Else, random

Phase 2 - Grahdens

Stats and Resistances

Actions per Turn: 3~4
HP: 4000000 ATK: 5500 DEF: 2000

Status Resistances:

• 70% resistant to Injury (prevents 2750 damage per attack)
• Immune to all other ailments

Crit Resistance:

• Base Crit Rate is 10% (no change)
• Value of all increases to crit are halved (50% multiplier)
• Base crit damage bonus is reduced by 10% (crits deal 145-154% damage)
• Crit damage cannot be increased by any method

Elemental Weakness Resistance:

• Base elemental weakness damage is reduced to 40%
• Immune to Elemental Weakness Damage bonuses

Spark Resistance:

• Base spark damage is 37.5%
• All spark damage bonuses are halved (50% multiplier)

BC/HC Resistance:

• None in this phase

Other Passives:

• 25% chance of healing 10-25% of damage taken

AI Summary

• "Now, show me that strength, will you?" is used on the first turn, acts as a warning for an HP->1 nuke buff wipe next turn
  • Inflict sickness to prevent. Sickness resistance is reduced to 0% during the warning period.
• 80% Threshold
  • Summons Febros
  • Buffs self 80% ATK/ 30% DEF until buff wiped (Buff wipes can be triggered by cancelling certain sequences)
• 60% Threshold
  • Summons Reud
• 50% Threshold
  • Starts 2 turn warning sequence, 80% mitigation for those 2 turns
    • Turn 1: "Your strength...give it to me..."
    • Turn 2: "Deliver the scream of skyward spirits!"
    • Turn 3: Criminal Lira - Large AoE 999 turn LS lock 100% BB drain
      • ~11k damage before DEF
  • Prevent by killing Febros
    • Febros must not be killed before this warning sequence
  • Killing Febros early will result in Grah getting buff wiped, but will make it impossible to prevent the nuke
• 30% Threshold
  • Summons Drevas
• Grah will count BB usage
  • If you use 4 BB, he'll use an AoE that causes BB drain and a BB fill rate debuff
    • ~7700 damage
  • If you use more than 4 BB, he'll use an AoE that causes 3 turn LS lock and a BB fill rate debuff
    • ~7700 damage
• Normal attack priorities:
  • 15% chance: Light unit
  • 20% chance: Units over 50% HP
  • Else, random

Phase 2 - Febros

Stats and Resistances

Actions per turn: 3
HP: 2000000 ATK: 5500 DEF: 3000

Status Resistances:

• 50% resistance to Weakness
• 25% resistance to Poison (200k damage per turn)
• Immune to all other ailments

Crit Resistance:

• Base Crit Rate reduced to 5%
• Value of all increases to crit chance are halved (50% multiplier)
• Crit damage bonuses reduced by 80% (20% multiplier)
• Base crit damage is untouched

Elemental Weakness Resistance:

• Elemental Weakness Damage bonuses reduced by 80% (20% multiplier)
• Base 50% is untouched

Spark Resistance:

• None

BC/HC Resistance:

• Base BC drop rate reduced to 26.25%
• Base HC drop rate reduced to 7.5%
• All BC/HC drop rate boosts are halved (50% multiplier)

Other Passives:

• None

AI Summary

• Grah passes 50% HP -> Overdrive
• 2 turns after Overdrive, UBB, then end turn
  • 19.2k damage, 50% ATK/DEF/BB ATK for Grah's squad for 3 turns
  • Only prevention method is to kill Febros before it fires
• 4 turn timer: SBB
  • 11.5k damage, 50% ATK and 20% ATK->DEF for Grah's squad for 3 turns
• 2 turn timer: BB
  • 8.5k damage, 30% ATK for Grah's squad for 3 turns
  • Cancelled by SBB, so BB and SBB alternate on even turns
• Normal attack priorities:
  • 20% chance: Lowest DEF
  • 25% chance: Units over 50% HP
  • Else, random

Phase 2 - Reud

Stats and Resistances

Actions per turn: 2~3
HP: 1400000 ATK: 5600 DEF: 2500

Status Resistances:

• 25% resistance to Sickness
• 25% resistance to Curse
• 50% resistance to Injury (-2800 damage per attack)
• Immune to all other ailments

Crit Resistance:

• Crit Chance buffs are halved (50% multiplier)
• Crit Damage boosts are reduced by 80% (20% multiplier)
• Base crit damage is untouched

Elemental Weakness Resistance:

• Elemental Weakness Damage bonuses are reduced by 80% (20% multiplier)
• Base 50% is untouched

Spark Resistance:

• None

BC/HC Resistance:

• Base BC drop rate reduced to 31.5%
• Base HC drop rate reduced to 9%
• All BC/HC drop rate boosts are reduced by 80% (20% multiplier)

Other Passives:

• None

AI Summary

• Grah passes 30% HP -> Overdrive
  • Only once
• 2 turns after Overdrive, UBB, then ends turn
  • About 17k damage, gives Grah squad 50% ATK/100k HP regen for 3 turns
  • Prevent with curse
  • Forced BB next possible turn if prevented
• 3 turn timer: SBB
  • 9.2-10.6k damage depending on buffs, gives Grah squad 25% ATK for 3 turns
  • Not used during OD sequence
• 15% chance on any normal attack: BB
  • 6.7-9.5k damage depending on buffs, gives Grah squad 10-20k HP regen for 3 turns
  • Not used during OD sequence
  • No limit
• Normal attack priorities:
  • Units over 50% BB gauge, 25%
  • Else, random

Phase 2 - Drevas

Stats and Resistances

Actions per turn: 3
HP: 1600000 ATK: 5000 DEF: 5000

Status Resistances:

• 50% resistance to Sickness
• 25% resistance to Weaken
• Immune to all other ailments

Crit Resistance:

• Base Crit Rate reduced to 7.5%
• Value of all increases to crit chance are halved (50% multiplier)
• Crit damage cannot be increased by any method
• Base 50% crit damage is untouched

Elemental Weakness Resistance:

• Immune to Elemental Weakness Damage bonuses
• Base 50% is untouched

Spark Resistance:

• None

BC/HC Resistance:

• Base BC drop rate reduced to 28%
• Base HC drop rate reduced to 7.5%
• All BC/HC drop rate boosts are halved (50% multiplier)

Other Passives:

• None

AI Summary

• Grah passes 15% HP: Overdrive -> No BB next turn -> UBB
  • Prevention: Kill Drevas before Grah
  • OD: 50% ATK/DEF self-buff for 3 turns
  • UBB: AoE, 3 turn Status Reflect (all 100% chance), 3 turn 80% ATK buff vs enemies with ailments
    • ~14.3k damage before DEF
• 5 turn timer: SBB - AoE, 3 turn Status Reflect (all), 2 turn 10% water/thunder mitigation, 3 turn ATK buff vs enemies with ailments
  • ~7.6k damage before DEF
• 2 turn timer: BB - AoE, 1 turn Null Ails, 3 turn Status Reflect (all), 2 turn 10% water/thunder mitigation
  • ~6.6k damage before DEF
• Normal attack priority:
  • 20% chance: Thunder units
  • 25% chance: Units over 50% BB gauge
  • Else, random

Phase 3 - Owen

Stats and Resistances

Actions per Turn: 3
HP: 7500000 ATK: 8000 DEF: 3000

Status Resistances:

• 70% Resistant to Injury (prevents 4000 damage per attack)
• 70% Resistant to Sickness
• Immune to all other ailments
  

Crit Resistance:

• Base Crit Rate is 9%%
• Value of all increases to crit are halved (50% multiplier)
• Base crit damage bonus is reduced by 10% (crits deal 145-154% damage)
• Crit damage cannot be increased by any method

Elemental Weakness Damage Resistance:

• Base elemental weakness damage is reduced to 40%
• Immune to Elemental Weakness damage bonuses

Spark Resistance:

• Base spark damage is 37.5%
• All spark damage bonuses are halved (50% multiplier)

BC/HC Resistance:

• 10% multiplicative penalty to total BC drop rate
• Base HC drop rate is 8.5%
• 25% multiplicative penalty to all HC drop rate boosts

Other Passives:

• 15% ATK boost after passing 50% HP
  • 1200-1230 increase to base damage of all non-DoT, non-HP% attacks (x2.1 for normals with hit count buff active)

AI Summary

• Item use is punished with AoE Buff Wipe 10k DoT, with exceptions:
  • The turn either Owen or Grah passes 50% HP (only the first time one of them passes 50%)
  • Disabled during Owen's Overdrive
  • If only 2 or 3 units are alive after item usage
• When Owen or Grah first pass 50% HP, there is a sequence in which he grants himself 80% mitigation and damage reflect for several turns. At the end of the sequence, he attacks with AoE 16k DoT Buff Wipe
  • Turn 1: "Hmm...very well! Back me up, then." - Gives himself 80% mitigation
  • Turn 2: "O burning spirit, in your body of steel!" - Gives himself 80% mitigation and 10-20% damage reflect
  • Turn 3: "Wicked spirits of all creation!" - Gives himself 80% mitigation and 10-20% damage reflect
  • Turn 4: "Now! Let's finish this!" - Gives himself 80% mitigation and 10-20% damage reflect
  • Turn 5: "Underworld Wyrm Volzeanos" - 12.3k AoE 16k DoT Buff Wipe
  • This sequence can be cancelled by dealing over 50000 damage to Grah and inflicting him with a status ailment in the same turn
    • If you do this, you also need to hit Owen for 50000 damage on the next turn, or he'll use an AoE 9.6k DoT Buff Wipe
  • It can also be theoretically cancelled by killing Grah
• Single Target BB Buff Wipe on highest HP unit at 90% HP
• Uses Overdrive at 15% HP, followed by UBB 2 turns later
• After passing 50% HP, using 4 or more BB in one turn triggers a ST buff wipe and small self-buff on Owen
• Major stat buffs once Grah dies; slightly more than doubles normal attack damage via a hit count buff and 15% total to BB mods
  • Buffs are permanent, all methods of buff-wiping Owen require Grah to be alive
  • Grah gets the same buffs if Owen dies first
• 6 turn timer from start of fight that can activate once Owen passes 80% HP, starts the following sequence:
  • Owen grants himself damage reflect for 1 turn
  • Owen grants himself 25% ATK, 50% DEF and 50% Crit Damage for 3 turns, but reduces his Injury Resistance by 50%
  • Owen attacks with an AoE with DoT attached to it. Damage is dependent on how much damage the player dealt in the previous turn - this is more dangerous if the player deals over 50000 damage
  • This DoT ranges from 8.4k to 9.6k damage depending on the version triggered
• 2 turn timer on his basic AoE, grants him and Grah 15% crit chance and causes Injury/Weaken
  • Interrupted by any scripted sequence except the first turn of Overdrive (Overdrive will begin the turn after instead)
• Normal attack priorities:
  • 20% chance of attacking units over 50% BB gauge
  • 25% chance of attacking units over 50% HP gauge (effectively equal chance to above)
  • Otherwise random

Phase 3 - Grah

Stats and Resistances

Actions per Turn: 3~4
HP: 7000000 ATK: 6500 DEF: 2500

Status Resistances:

• 90% Resistant to Injury (prevents 3250 damage per attack)
• 40% Resistant to Sickness
• Immune to all other ailments
  

Crit Resistance:

• Base Crit Rate is 8%
• Value of all increases to crit are halved (50% multiplier)
• Base crit damage bonus is reduced by 10% (crits deal 145-154% damage)
• Crit damage cannot be increased by any method

Elemental Weakness Damage Resistance:

• Base elemental weakness damage is reduced to 40%
• Immune to Elemental Weakness Damage bonuses

Spark Resistance:

• Base spark damage is 37.5%
• All spark damage bonuses are halved (50% multiplier)

BC/HC Resistance:

• Base BC drop rate is 31.5%
• 50% multiplicative penalty to all BC drop rate boosts
• Base HC drop rate is 9%
• 20% multiplicative penalty to all HC drop rate boosts

Other Passives:

• 20% ATK boost after passing 50% HP
  • 1300 increase to base damage of all non-DoT, non-HP% attacks (x2.15 for normals with hit count buf factive)

AI Summary

• 70% and 40% HP: Grants himself ATK, DEF, DEF Ignore and himself and Owen status reflect (all ailments) for 3 turns
  • Next turn uses either an AoE Light/Dark buff Shield (if hit for at least 50000 on your turn) or AoE LS Lock (3 turns) BB Fill Rate debuff (if hit for under 50000 on next turn)
• When either Grah or Owen pass 50% HP, Grah will enter a 5 turn sequence
  • Turn 1: "Hey Owen, it's time for you-know-what!" - AoE inflict BB mod debuff
  • Turn 2: "Spirits who find solitude in darkness!" - AoE 80% mitigation
  • Turn 3: "Spirit of Steel!" - AoE 80% mitigation
  • Turn 4: "Take this!" - AoE 80% mitigation
  • Turn 5: "Underworld Wyrm Volzeanos!" - AoE 999 turn LS lock 100% BB drain
  • This sequence can be aborted by dealing 50k damage to Grah within a single turn and inflicting an ailment on him, in which case he'll just buff wipe himself. This action also aborts Owen's side of the sequence.
  • Recommended to focus on Grah as stopping him also stops Owen, but not vice-versa. Easiest to deal 50k damage on the first turn, but Grah has increasing paralysis vulnerability through the 2nd, 3rd and 4th turns.
  • Additionally, during this time Grah and Owen won't punish UBB/BB spam or item usage.
• When over 50% HP, he'll use an AoE 999 turn LS Lock -80% BB Fill Rate debuff if the player uses a UBB
• When under 40% HP, he'll use an AoE LS Lock BB Fill Rate debuff if the player uses 4 or more BB within a single turn
• 30% HP: Grants himself and Owen status reflect (all ailments) for 3 turns
• 15% HP: Activates Overdrive
  • 2 turns later: UBB (Massive AoE 100% light/dark regen 2 turns 99-100k HP regen 3 turns
  • Next turn restarts the sequence with another Overdrive
• If Owen dies, Grah will get a massive buff to normal attacks (215% damage via hit count buff) and a small boost to ATK and BB mod for the rest of the fight
• 4 turn timer: AoE 75% BB drain -50% BB fill rate debuff
  • If Grah has any ailment, he'll use AoE light/dark buffs 10k HP Dark Barrier instead
• 3 turn timer: AoE light/dark buffs 10k HP Dark Barrier
  • Interrupted by every single action above this
• 20% chance per turn: AoE light/dark buffs 50% ATK/DEF down resistance (1 turn)