Blossombeast

Refer to https://pastebin.com/KTktriKy.

HP 100%-51%: Vine Grab: Head->Vine Grab: Arm->Vine Grab: Leg.
HP 50%: Suspicious Pollen.
HP 50-1%: 2-3 turns of A->Suspicious Pollen. A is any of the Vine Grab moves. The chance of using only 2 turns of A is 30%.

Berserker King

Unlike EO4, you cannot prevent Berserker Rage by doing enough damage while charging.

Turn 1: Binding Voice
HP 100-91%: Attack or Ruinous Strike
HP 90-71%: Charge->Berserker Rage->Berserk(->Attack*3)->A->A; A is either normal Attack or Ruinous Strike. The normal Attacks after Berserk will only be executed while Berserk buff is active.
HP 70-51%: Charge->Berserker Rage->Berserk(->Attack*3)->B->B. B is either normal Attack, Ruinous Strike or Arm Breaker.
HP 50-1%: Charge->Berserker Rage->Berserk(->Attack*3)->C->C. C is either normal Attack, Ruinous Strike, Arm Breaker or Rock Crusherer.

Binding Voice has a low chance of being used on any turn.
Since the first battle starts at 50% HP, it will start off with the lowest pattern.


Cernunnos

Turn 1: Silent Stare
Turn 5n: Always Cross Counter. Has priority over Call Ally.
Otherwise:
HP 100-81%: Either normal Attack, Combo Smash or Silent Stare
HP 80%: Call Ally
HP 80-51%: Either normal Attack, Combo Smash, Hurricane Punch or Silent Stare.
HP 50%: Call Ally
HP 50-21%: Either normal Attack, Combo Smash, Hurricane PUnch, Silent Stare or Fire Rush. Fire rush is used more commonly than others?
HP 20%: Call Ally
HP 20-1%: Either Combo Smash, Hurricane Punch, Silent Stare or Fire Rush.


Wyvern

On the first battle, you start with a pre-emptive, and whenever you have a character die, Wyvern may be stunned on the next turn (it seems that this is guaranteed on the first occurance and drops from there; by the fourth time it barely happens at all).

HP 100-91%: Either normal Attack or Wing Talon or Burning Ray.
HP 90-51%: Brilliant Breath->Whirlwind->A->A->A->A. A is either normal Attack, Wing Talon or Burning Ray. Brilliant Breath is an all-targeting volt attack.
HP 50-26%: Brilliant Breath->Whirlwind->B->B->B->B. B is either normal Attack, Wing Talon, Burning Ray or Tail Strike.
HP 25-1%: Brilliant Breath->C->C->C->C. C is either Wing Talon, Burning Ray, Tail Strike or Whirlwind.


Silurus

Unlike EO3 Narmer, Silurus will heal itself while dived until you hit the correct hole, at which point it will use Earthquake at the end of the turn.

HP 100-91%: Either normal attack, Whip Ripper or Mud Throw.
HP 90%: Dive (2 holes)->Earthquake
HP 90-76%: A->A->A->A->Dive (2 holes)->Earthquake. A is either normal attack, Whip Ripper or Mud Throw.
HP 75%: Dive (3 holes)->Earthquake
HP 75-51%: B->B->B->B->Dive (3 holes)->Earthquake. B is either normal attack, Whip Ripper, Mud Throw or Fin Smack. Fin Smack is now a spread-target bash attack that lowers elemental defense.
HP 50%: Dive (4 holes)->Earthquake
HP 50-26%: C->C->C->Dive (4 holes)->Earthquake. C is either normal Attack, Whip Ripper, Mud Throw, Fin Smash or Head Smack. Head Smack is a single-target bash attack that may inflict panic.
HP 25%: Dive (6 holes)->Earthquake
HP 25-1%: 2-5 turns of C->Dive (6 holes)->Earthquake.

Shellbeast

Attacks:
Dark Flame: Uses the head. Deals ranged fire damage to all party members. May inflict blind.
Dark Slice: Uses the arms. Deals melee cut damage to a row of party members. May inflict curse.
Death Glow: Uses the head. May inflict instant death to all party members.
Toxic Mist: Uses the legs. May inflict poison to all party members. The poison ticks for ~30 damage.
Thousand Hertz: Uses the head. May inflict Head Bind and Stun to all party members.

Summon: Midnight Skull
Dark Mist: Co-op skill that requires two Midnight Skulls. Uses the head. Inflict a debuff that prevents binds or ailments from being removed for 4 turns.

HP 100-91%: Dark Flame[->Dark Slice]->normal Attack. Dark Slice may or may not be used.
HP 90%: Death Glow. Call Allies will be used at the end of next turn, and every 5 turns thereafter.
HP 90-76%: Dark Flame[->Dark Slice]->normal Attack.
HP 75%: Toxic Mist
HP 75-51%: Dark Flame[->Dark Slice][->Toxic Mist]->Normal Attack.
HP 50%: Thousand Hertz->Toxic Mist
HP 50-26%: Dark Flame[->Dark Slice][->Toxic Mist][->Thousand Hertz]->normal Attack.
HP 25%: Death Glow
HP 25-1%: Either Dark Flame, Toxic Mist or Thousand Hertz.

If you do enough damage, you can skip the HP-based fixed moves. For example, taking it down below 75% immediately will skip Death Glow. The first Call Allies is always used after Death Glow, so you can skip it by skipping Death Glow this way as well, but it will still be used every 5 turns thereafter.


Harpuia

Feast's hit count is now fixed at 2-4 instead of increasing as it is used.

HP 100-76%: Blood Offering->Shrill Cry->A->A->A. A is Claws of Despair->normal Attack. Blood Offering is a new attack that deals ranged cut damage to all party members, which deals greatly increased damage to ailed or bound targets. Shrill Cry now inflicts Panic rather than Fear.
HP 75%: Chaos Scream at the end of turn->Storm Feathers. Harpuia will still use Blood Offering first if she is scheduled to use that.
HP 75-51%: Blood Offering->Shrill Cry->B->B->B. B is either Storm Feathers, Claws of Despair or normal Attack.
HP 50%: Chaos Scream at the end of turn->Feast.
HP 50-26%: Blood Offering->Shrill Cry->C->C->C. C is either Feast, Storm Feathers, Claws of Despair or normal attack.
HP 25%: Chaos Scream at the end of turn->Starts at D on the next turn
HP 25-1%: Blood Offering->D->D->D. D is either Storm Feathers, Feast, Claws of Despair or Shrill Cry.

Chimaera

Two new moves:
Evil Strike: Uses the arms. Deals melee cut damage 3-7 times to random party members. May inflict Curse.
Summon Underling: Uses the head. Causes Vampire Bats on the floor to turn aggressive and start moving to join the battle.

Turn 1: Snake Pile->Summon Underling at the end of turn. Summon Underling will be used at the end of turn every 4 turns thereafter.
HP 100-91%: Normal Attack->Snake Pile.
HP 90%: Double Strike.
HP 90-76%: A->A->A->Snake Pile. A is either normal Attack or Double Strike.
HP 75%: Great Blaze.
HP 75-51%: Random number of turns of B->normal Attack->Great Blaze. B is either Double Strike or Snake Pile, with Double Strike being significantly more likely.
HP 50%: Evil Strike
HP 50-26%: Random number of turns of C->normal Attack->Evil Strike. C is either Double Strike, Snake Pile or Great Blaze, with Double Strike being significantly more likely.
HP 25%: Double Strike
HP 25-15: Either Snake Pile, Great Blaze or Evil Strike. Double Strike will no longer be used.

Ketos

Ocean Rave and Grand Bury now use the arms rather than the head. Has a new move (Ancient Undulation) which uses the legs, grants Ketos an accuracy buff and inflicts evasion debuff on all party mmebers for 3 turns.

Start: Spout->Ocean Rave. Spout will be used every 8 turns until Ketos's HP is bleow 50%, but Ocean Rave takes priority over it.
HP 100-76%: A->A->Ocean Rave->A->A. A is either normal Attack or Grand Bury, though Ketos is very likely to alternate between them.
HP 75%: Ancient Undulation->Ocean Rave.
HP 75-51%: B->B->B->B->Ocean Rave. B is either normal Attack, Grand Bury or Freeze Ripple.
HP 50%: Grand Melody. Spout will no longer be used from this point on.
HP 50-26%: C->C->C->C->Ocean Rave. C is either normal Attack, Grand Bury, Freeze Ripple or Grand Melody.
HP 25%: Ancient Undulation->Ocean Rave.
HP 25-1%: D->D->D->D->Ocean Rave. D is either normal Attack, Grand Bury, Freeze Ripple, Grand Melody or Ocean Rave.


Insectbeast

Attacks:
Freezestorm: Uses the arms. Deals ranged ice damage 2-5 times to random party members. Each party member can be hit once at most. Debuffs attack by 50% for 3 turns.
Thunderstorm: Uses the arms. Deals ranged volt damage to all party mmebers.
Skewer: Uses the legs. Deals stab damage to one party member, with line piercing effects. Debuffs accuracy for 3 turns.
Pierce Strike: Uses the legs. Deals stab damage to one party member, with spread damage. May inflict Arm Bind.
Safeguard: Uses the arms. Buffs defense by 75% for 3 turns.
Repair Mode: Turns user into self-repair mode.
Self Repair: Uses the arms. Heals the user for 1250 HP, and removes all debuffs, ailment or binds.
Curse Gas: Uses the head. May inflict curse to all party members.
Petrify Gas: Uses the head. May inflict petrify to all party members.
Chaos Gas: Uses the head. May inflict panic to all party members.

Repair Mode will cause Insectbeast to use nothing but Self Repair for the next 3 turns, or until it is broken by damage (around 1500). Unlike Hippogryph, Repair Mode doesn't give the user any defense bonus.

Turn 1: Thunderstorm
HP 100-91%: Normal Attack->Thunderstorm[->Skewer]. Skewer is not used very often.
HP 90%: Safeguard. Safeguard will be used every 4 turns thereafter, but has low priority and may be delayed for a turn.
HP 90-76%: Normal Attack->Thunderstorm[->Skewer].
HP 75%: Repair Mode at the end of turn.
After Repair Mode wears off: Freeze Storm->Curse Gas at the end of turn. Curse Gas will be used at the end of turn every 3 turns thereafter.
HP 75-51%: Either A mode or B mode. A mode is normal Attack->Thunderstorm, B mode is Skewer->Freezestorm. Insectbeast will alternate between them.
HP 50%: Repair Mode at the end of turn.
After Repair Mode wears off: Pierce Strike->Petrify Gas at the end of turn. Petrify Gas will be used at the end of turns every 3 turns thereafter. (Curse Gas will no longer be used?)
HP 50-31%: Either A mode or B mode. A mode is normal Attack->Thunderstorm, B mode is Skewer->Freezestorm->Pierce Strike. Insectbeast will alternate between them.
HP 30%: Repair Mode at the end of turn.
After Repair Mode wears off: Random action->Chaos Gas at the end of turn. Chaos Gas will be used at the end of turns every 3 turns thereafter. (Petrify Gas will no longer be used?)
HP 30-1%: Either A mode or B mode. A mode is normal Attack->Thunderstorm, B mode is Skewer->Freezestorm->Pierce Strike. Insectbeast will alternate between them. Safeguard now takes about twice as long to reuse.


Salamander

Salamander will still summon Baby Salamanders, but will no longer use Inferno Rounds when they are killed. It also learns a new move (Selfless Love) which uses the arms, and causes all attacks targeted at Baby Salamanders to be redirected to Salamander until the end of next turn. Healing Cry will only heal 1500 HP. Also,

Turn 1: Hellfire Breath
Will basically repeat Hellfire Breath->random numbers of turns of (either normal Attack, Claws of Avarice or Crushing Tail) for the rest of the fight. Crushing Tail is only used at below 50%, unless one of the following moves are scheduled.

HP 91%: Call Ally (1)
HP 81%: Call Ally (1)->Selfless Love
HP 71%: Call Ally (2)->Selfless Love
HP 61%: Call Ally (2)->normal Attack->Selfless Love
HP 51%: Call Ally (2)->Crushing Tail
HP 41%: Call Ally (2)->Selfless Love
HP 31%: Call Ally (3)->Healing Cry->Selfless Love
HP 21%: Call Ally (3)->Selfless Love
HP 11%: Call Ally (4)->Selfless Love

Call Ally is always used at the end of turn. Number in bracket denotes the number of Baby Salamanders called.


Boiling Lizard

Fireball Cannon now deals 2-5 hits regardless of temperature and may inflict blind. Learns a new move (Sleep Tail) that inflicts melee stab damage to a row and may inflict sleep. Instead of destroying Scales with Icy Stakes, now they are frozen by ice moves (and Miasma Tsunami), which will cause them to take damage normally until they thaw out.

HP 100-76%: Scorching Fire->A->A->1 Scale. A is either normal Attack, Fireball Cannon or Upward Thrust.
HP 75-51%: Scorching Fire->B->B->1 Scale. B is either normal Attack, Fireball Cannon, Upward Thrust or Sleep Tail.
HP 50%: Fire Wall
HP 50-26%: Scorching Fire->B->B->2 Scales.
HP 25%: Revival Fire
HP 25-1%: Scorching Fire->C->C->3 Scales. C is either Fireball Cannon or Upward Thrust or Sleep Tail. If weakened by breaking scale beforehand, Boiling Lizard will still only summon 2 Scales.


Basilisk

Learns a move (Raging Howl) that uses the head and debuffs all party member's attack by 50%, as well as possibly inflicting stun. Basilisk Eyes will use Stone Gaze 3 turns after appearing the first time, 2 turns after appearing the second time, and every turn thereafter. Doom Breath debuffs maxHP by 25%.

HP 100-81%: Normal Attack or Dark Moon.
HP 80%: Basilisk Eyes appear.
HP 80-51%: (Normal Attack->Impairing Claws) or Dark Moon. Dark Moon is used infrequently.
HP 50%: Doom Breath->Raging Howls. Doom Breath will be used every 7-9 turns thereafter.
HP 50-31%: (Normal Attack->Impairing Claws) or Dark Moon. Dark Moon is used infrequently.
HP 30%: Basilisk Eyes appear.
HP 30-1%: Dark Moon->Pound->Normal Attack->Imparing Claws. However, Raging Howl and Doom Breath may randomly be used instead.


Iwaoropenelep

Pinion Spear now hits 7 times. Learns a new move (Intimidating Wind) that uses the arms and buffs its physical attack by about 50% for 3 turns.

Start: Thunderwing->Pinion Spear
HP 100-76%: Thunderwing->A->A->A->A. A is either (normal attack->Pinion Spear) or Deathbringer.
HP 75%: Intimidating Wind at the end of turn. Intimidating Wind will be used at the end of turns every 4 turns thereafter.
HP 75-51%: Thunderwing->B->B->B->B. B is either (normal attack->Pinion Spear), Deathbringer or Grip.
HP 50%: Wind Breath. It will be used every 6-8 turns thereafter.
HP 50-26%: Thunderwing->B->B->B.
HP 25%: Chaosbringer.
HP 25-1%: Thunderwing->C->C->C. C is either Pinion Spear, Deathbringer, Grip or Chaosbringer.


Brod

Refer to https://pastebin.com/xh4xC5i5

HP 100-81%: Wide Bravery->Abominable Wave->Wide Bravery->Clear Mind Ex->Guard Rush Ex. May use a normal attack in place of a Wide Bravery (40%), and Clear Mind Ex will be skiped if it isn't needed.
HP 80-51%: (Normal Attack(40%) or Wide Bravery(60%))->(Wide Bravery (40%) or Abominable Wave(60%))->Frigid Slash Ex->Clear Mind Ex->Guard Rush Ex. Clear Mind Ex will be skiped if it isn't needed.
HP 50-31%: Act Breaker->Abominable Wave->Frigid Slash Ex->Clear Mind Ex->Guard Rush Ex. Act Breaker and Frigid Slash Ex may be replaced with Wide Bravery (40%, never for first Act Breaker), and Clear Mind Ex will be skiped if it isn't needed.
HP 30-1%: A->A->Miracle Edge Ex. A is either Wide Bravery(20%), Guard Rush Ex(15%), Frigid Slash Ex(35%) or Act Breaker(30%).


Jormungandr

Refer to https://pastebin.com/15qTunR6

Jourmungandr will only change phase after changing back from Tail Mode and going through Sealed Light.

Turn 1: Weakening Flash.
HP 100%-81%: Megalo Dive->normal Attack->Eye of Resentment + change Mode at end of turn->Pendulum Tail->Sealed Light
HP 80-51%: (Clean Sweep(30%), Weakening Flash(50%), or Megalo Dive(20%))->(Clean Sweep(60%) or Megalo Dive(40%))->Eye of Resentment + change Mode at end of turn->Pendulum Tail->Sealed Light. Will always use Clean Sweep on the first turn of first cycle.
HP 50-31%: (Power Press(30%), Weakening Flash(50%), Clean Sweep(10%), or Megalo Dive(10%))->(Clean Sweep(70%) or Megalo Dive(30%))->Eye of Resentment + change Mode at end of turn->Pendulum Tail->Sealed Light. Will always use Power Press on the first turn of first cycle.
30%-1%: (Sealing Flame(30%), Power Press (40%) or Weakening Flash (30%))->(Clean Sweep(70%) or Megalo Dive(30%))->Eye of Resentment + change Mode at end of turn->Pendulum Tail->Sealed Light. Will always use Sealing Flame on the first turn of first cycle.