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Forgotten OneHardmode exclusive
Abyssion, The Forgotten One
Statistics
TypeBossAquatic
EnvironmentAquatic Depths
AI TypeForgotten One AI
Damage80 / 160
Max Life60,000 / 84,000
Defense0
KB Resist100%
Immune toCrowd ControlPoisonedVenom
Drops
Coins150000*15 Gold Coin

Forgotten One is a Hardmode, post-Plantera boss fought in the Aquatic Depths. The boss has multiple forms, each more powerful than the last.

While The Forgotten One is alive, its exclusive Music will play.

Spawn[ | ]

The Forgotten One does not spawn on its own and requires the player to kill Aquatic Hallucinations in the Aquatic Depths. They will drop Abyssal Shadows, which will inflict the False Presence debuff once for every one picked up. Upon reaching three stacks of the debuff, The Forgotten One will emerge. Multiple Forgotten Ones cannot be summoned through this process.

After The Forgotten One has been defeated in the world at least once, Abyssal Shadows will behave like normal Summoning items, summoning the boss on use.

Forms[ | ]

Forgotten OneCrackedHardmode exclusive
Abyssion, The Forgotten One (Cracked)
Statistics
TypeBossAquatic
EnvironmentAquatic Depths
AI TypeForgotten One AI
Damage80 / 160
Max Life30,000/60,000 / 55,500/84,000
Defense0
KB Resist100%
Immune toCrowd ControlPoisonedVenom

Behavior[ | ]

Attacks[ | ]

  • If the player is not in a body of water, it will enrage in a manner similar to Plantera. While enraged, it moves at a higher velocity, summons Abyssal Spawns more often, and its spit projectiles will home in on the player.
  • The Forgotten One slowly follows the player, attempting to swim into them. It will also periodically fire wall-piercing whirlpool projectiles.
  • Immediately at 85% life and occasionally below it, The Forgotten One will occasionally hide within its shell, causing it to take 1 damage per hit. When in its shell, it will rapidly shoot at the nearest player with fast moving and heavy damaging spit projectiles.
  • At 50%/66% life, The Forgotten One's shell cracks as it enters its second phase, immediately launching its shell attack and gaining numerous changes.
    • Starts periodically shooting pairs of projectiles together; water ripples that bounce along walls, and semi-homing dark magic slashes that attempt to block player movement.
    • The Forgotten One's shell attack can be used much more frequently, but only reduces damage by roughly 50%. It can also use all of its other regular attacks while in its shell, as well as summoning 5 Abyssal Spawn whenever it enters this attack.
  • At 33% life in Expert Mode, The Forgotten One transforms into its third phase.

Summons[ | ]

Image Name Condition
Abyssal Spawn Abyssal Spawn Below 50%/66% life

In Expert Mode[ | ]

Forgotten OneReleasedHardmode exclusive
Abyssion, The Forgotten One (Released)
Statistics
TypeBossAquatic
EnvironmentAquatic Depths
AI TypeForgotten One AI
Damage160
Max Life27,700/84,000
Defense30
KB Resist100%
Immune toCrowd ControlPoisonedVenom
Expert Mode-Only Content: This information applies only to Expert mode and Expert mode worlds.

Abyssion Trophy "The Forgotten One breaks free of its ancient prison!" Abyssion Trophy

Forgotten One (Released) is the Expert Mode exclusive final phase of the encounter. The transformation is notified with the status message, "The Forgotten One breaks free of its ancient prison!"

Behavior[ | ]

  • Movement speed increased by roughly 50%.
  • The Forgotten One immediately uses its spit attack after entering this phase.
  • The Forgotten One retains all previous attacks, but with a few changes:
    • Spit attack fires more shots and purple shots that deal increased damage, but The Forgotten One no longer reduces incoming damage while using the attack.
    • Fires three dark magic slashes at once, which are also purple and inflict much higher damage.

Aftermath[ | ]

  • Upon defeating The Forgotten One for the first time, the Aquatic Depths biome's Choking Aura debuff will be replaced with the Untainted Waters buff, allowing them to breathe water and air in the biome without taking damage. This is indicated with the message upon its defeat "The toxic haze of the depths has been lifted..."
  • The Diverman will start selling The Whirlpool.

Trivia[ | ]

  • Forgotten One resembles a large Parapaguridae hermit crab, an aquatic crab that lives in deep water.

History[ | ]

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