The indescribable god has awakened!
Beginning of Abyssal God's second phase, Etrian Odyssey III: The Drowned City

Abyssal God full body

Abyssal God is the true final boss of Etrian Odyssey III: The Drowned City.

It's fought on B25F, the final floor of the Yggdrasil Labyrinth, and is arguably the hardest boss in the game.

This creature is the final enemy of the explorers, the creator of the Deep Ones. No words can describe this colossal, tentacle ridden abomination. Its only visible part is its head, atop its body, with a huge, gaping maw.

This beast has many forms of attacks. When its mouth is closed, it uses its tentacles to defend itself, countering any incoming attack and draining the offender's health, to restore its own. However, once it opens its mouth and shows its true form, it attacks with unstoppable rage, using powerful elemental spells and its huge tentacles, ripping apart anything that dares to oppose its might.


Spoiler Warning: Plot details follow. Read at your own risk.
The Abyssal God is a power-hungry god-like alien being that travels around space, seeking planets to conquer. It creates a new race on it, acting like an invasive species, destroying other predominant life forms until the race becomes the predominant one (with the races created by the Abyssal God also worshipping it as a deity). It went unstoppable for eons until another being, known as the Yggdrasil Tree, a sentient, highly powerful tree, started chasing after it in order to put an end in its rampage. In order to escape the creature landed on the earth, where it found refuge under its vast oceans and soon created a new race, the Deep Ones, in order to start a war with the planet's dominant race, humans. However, the Yggdrasil soon followed its lead, and landed on the same spot as the monster, quickly growing roots and sealing it within a labyrinth. Now sealed deep into the sea, it simply lies in wait for an opportunity to finally break free and restart the cycle of destruction.


Before the battle starts, it's highly recommended to destroy the several tentacles scattered around the floor, as for each tentacle killed prior to the battle, a portion of its HP will be automatically depleted in the start of the fight. With all of them killed, it will start with around 3000 HP left, making the first phase of the fight much easier and faster. Plus, its defensive power will be lowered, so that you can kill it on a turn or two. Be careful however, as each turn it has a chance of reviving one of its tentacles, recovering 1000 HP and regaining some of its lost defenses.

Phase 1Edit

Abyssal God
Abyssal god 1
Enemy Data
HP 10000
AT ?
DF ?
Skills Magma Ocean, Ice Tempest, Proton Thunder
Items None
Weakness None
Resistance None
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The battle itself has two stages. On the first one, it uses 3 elemental attacks on the party (Magma Ocean, Ice Tempest and Proton Thunder) for massive damage (around 1000+ damage). The best thing is to use anti-elemental skills or elemental prophecies (preferably the latter, since it damages the boss) to nullify damage to the party. Be careful, because, if you didn't kill every tentacle, its attack pattern will change. However, if you didn't kill any tentacle at all, or you killed every one of them, it will have the following pattern: [Fire > Ice > Volt] This means you can easily keep track of which anti-elemental skill to use.

If you skipped the tentacles, the boss will have some huge defensive power, being almost impossible to kill. Killing all of the tentacles, though, will cause the monster to have ridiculously low defenses, making it easy to kill in a turn or two. Anyhow, depleting its HP will finish this phase it will proceed to the second one.

Phase 2Edit

Abyssal God
Abyssal god 2
A being that traversed space and time through an otherworldly sea. It awaits its awakening...
Enemy Data
HP 60000
AT 85
DF 71
EXP 300000
Skills Demon Rage, Chaos Tentacle, Rising Claw
Items Darkstar Bead
Weakness None
Resistance Physical Attacks
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The second stage is where the fight starts to get hard. Now, it has several new attacks (not just elementals this time), hits hard, and has a great deal of HP. On top of that, it will continuously change between its two forms: the defensive form (closed mouth), where it has increased defenses and will focus on recovering its HP and countering attacks, and the offensive form (open mouth), where it will abandon its defenses but receive extremely high attack power and make use of its most powerful moves. In the beginning of the fight, it has a clear attack pattern, that is as follows:

Nameless Wall > Mist Curtain > Chaotic Beckon > Spourting fumes > Abyssal offering > Form change > Demon Rage > Rising Claw > Chaos Tentacle > Primitive Burn > Foul Glacier > Dark Lightning > Form change > Abyssal offering > Nameless Wall >....

However, as soon as its HP reaches around 45,000, this pattern will change drastically. It will soon change into its defensive phase again, no matter at what stage of the pattern it is, and will start using its counter skills at random. This is extremely dangerous, especially for those who use multi-hitting skills. A well-placed counter will mean instant game over for sure, so this phase is, pretty much, luck based. It can use Chaotic Beckon occasionally, and every few turns, Abyssal Offering. If it, somehow, manages to fully recover its HP, the boss will reset the pattern, as if the battle was re-started. After spending a few turns on the defensive phase, or enough damage has been done it will change into the offensive one. After this point, it will be able to freely change between each phase.

Attack listEdit

(O) means it uses the attack in the offensive mode, (D) means it uses in the defensive one

  • Nameless Wall (D): Powerful counter-attack if hit with physical damage.
  • Mist Curtain (D): Powerful counter-attack if hit with elemental damage.
  • Chaotic Beckon (D): Heavy damage to everyone. Recover part of the damage to the hp of the boss.
  • Spourting Fumes (D): If damaged during the turn, will inflict random status effects to the whole party. This skill works on both physical and elemental skills, and is extremely dangerous. Can inflict petrify, and a plague status that deals over 300 damage per-turn.
  • Abyssal Offering (D): Remove all debuffs from abyssal god and recovers 11,475 HP from it.
  • Demon Rage (O): Attacks the party at random, dealing heavy damage each hit and removing buffs from the target. Very dangerous attack, use everytime it changes into the offensive stage.
  • Rising Claw (O): Heavy damage to the whole party.
  • Chaos Tentacle (O): Heavy damage. Always uses on the character with lowest hp.
  • Primitive Burn (O): Deals massive fire elemental damage to the whole party and debuffs the attack power.
  • Foul Glacier (O): Massive ice elemental damage to the whole party.
  • Dark Lightning (O): Massive volt elemental damage to the whole party and inflicts sleep.



  • The Abyssal god and the entirety of the Cyclopean Haunt have numerous of references to the Cthulhu Mythos. In fact, it may be Cthulhu itself, taking into account the number of references and similarities:
    • The Cyclopean Haunt, where the Abyssal God is found, has several references to R'lyeh, where Cthulhu lies sleeping.
    • They are both worshiped by an aquatic species called the Deep Ones (Etrian | Lovecraft)
    • The B25F title, "That which can eternal lie". is a direct reference to a quote in one of H.P. Lovecraft's writings "That is not dead which can eternal lie", which refers to Cthulhu.
  • This is the first optional final boss of the series that got its own battle theme (Primevil used the standard boss battle music and Ur-Child used the Overlord's theme). It's called "Calling that Detestable Name".
  • This is the first boss in the series to have a fully animated background, not related to the stratum theme.
  • This final boss, to some extent, broke the series tradition of optional final bosses having an attack pattern. It does have an attack pattern, but only in the start of the fight. As it closes to the end, it goes beserk and starts attacking you at random.
  • Its first phase is somewhat similar to the Yggdrasil Core, which may hint at a similarity between the two.


Calling that Detestable Name03:29

Calling that Detestable Name

Abyssal God's theme song

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