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PolterghastPhase 1
AI TypePolterghast AI
Damage150 / 240 / 360 (melee)
120 / 168 (hook)
110 / 184 / 276 (blue dart)
Max Life550,000 / 880,000 /
1,056,000 / 1,408,000
Defense (DR)150 (50% DR)
KB Resist100%
Immune toAll debuffs except:
Ichor (debuff)Cursed InfernoAbyssal FlamesDemon FlamesGod Slayer InfernoNightwitherShred
Polterghast map.png
Map Icon
NecroghastPhase 2
AI TypePolterghast AI
Damage180 / 288 / 302 / 432 (melee)
120 / 168 / 176 / 252 (hook)
120 / 196 / 205 / 294 (red dart)
130 / 216 / 226} / 324 (red blast)
Max Life412,500 / 550,000
660,000 / 880,000
792,000 / 1,056,000
1,056,000 / 1,408,000
Defense (DR)100 (55% DR)
KB Resist100%
Immune toAll debuffs except:
Ichor (debuff)Cursed InfernoAbyssal FlamesDemon FlamesGod Slayer InfernoNightwitherShred
NecroplasmPhase 3
AI TypePolterghast AI
Damage210 / 336 / 352 / 504 (melee)
120 / 168 / 176 / 252 (hook)
140 / 232 / 243 / 348 (spirit orb)
Max Life181,500 / 550,000
290,400 / 880,000
528,000 / 1,056,000
704,000 / 1,408,000
Defense (DR)0 (0 or 30% / 60 or 90% DR)
KB Resist100%
Immune toAll debuffs except:
Ichor (debuff)Cursed InfernoAbyssal FlamesDemon FlamesGod Slayer InfernoNightwitherShred

Polterghast Trophy.png "Shrieks are echoing from the Dungeon..." Polterghast Trophy.png

The Polterghast is a post-Moon Lord boss that is fought in the Dungeon. It is notable for being the only optional post-Moon Lord boss. However, given the strong equipment that it grants access to upon its defeat, it is recommended to fight it before challenging The Devourer of Gods.

Summoning[edit | edit source]

Polterghast can be summoned by using a Necroplasmic Beacon in the Dungeon. Alternatively, if it has not yet been defeated in the world, it will spawn after killing 30 Phantom Spirits, which can be found in the Dungeon after Moon Lord has been defeated. After defeating it once, using a Necroplasmic Beacon becomes the only way to summon the boss.

Behavior[edit | edit source]

Polterghast initially behaves similarly to Plantera, chasing the player quickly while using four long appendages to grapple blocks. In later phases, however, these appendages will detach and begin firing projectiles independently.

Phase 1 (Polterghast)[edit | edit source]

  • Polterghast follows a Plantera-like behavior, placing its hooks on nearby walls to pull itself towards the player.
  • While chasing the player, Polterghast steadily fires fast-moving blue projectiles which bounce off of walls.
  • Transforms into Necroghast at 75% health.

Phase 2 (Necroghast)[edit | edit source]

  • Necroghast's hooks detach from their chains, and they begin independently moving and shooting ghostly projectiles at the player.
  • Necroghast moves faster and deals more melee damage.
  • Necroghast's projectiles are now red instead of blue. Red projectiles travel faster, further, and deal slightly more damage. It also shoots bigger wall-piercing projectiles that slightly home into the player.
  • Transforms into Necroplasm at 33% / 50% health.

Phase 3 (Necroplasm)[edit | edit source]

  • Necroplasm summons a weaker clone of itself, which acts independently of Necroplasm and chases the player with more intensity. Necroplasm will summon a new clone 10 seconds after the previous is killed, and only one clone can exist at a time.
    • While the clone is alive, Necroplasm's DR is boosted by 30%.
  • Necroplasm stops firing projectiles directly. Instead, it summons three invincible Phantoms which slowly revolve around the player. The Phantoms fire spirit orbs which are initially slow, but quickly accelerate toward the player.
  • Necroplasm moves significantly faster and deals even more melee damage.
  • Necroplasm's hooks move slower and less often.
  • When below 20% / 33% health, Necroplasm begins summoning Happy Phantom Spirits, which also fire ghostly projectiles at the player.
  • When below 5% / 10% health, Necroplasm starts moving much faster as a last-ditch effort to attack the player.

In Revengeance Mode[edit | edit source]

  • Polterghast is faster in all three phases.
  • Transitions into Phase 3 (Necroplasm) at 50% health instead of 33%.
  • Spawns Happy Phantom Spirits at 33% health instead of 20%, and spawns even more of them.
  • Moves much faster at 10% health instead of 5% health.
  • Phantoms shoot more often.

Summons[edit | edit source]

AI TypePolterghast AI
Damage210 / 336 / 504
Max Life130,000 / 208,000 /
240,000 / 360,000
Defense 0
KB Resist100%
Immune toAll debuffs except:
Ichor (debuff)Cursed InfernoAbyssal FlamesDemon FlamesGod Slayer InfernoNightwitherShred
AI TypePhantom AI
Damage0 (contact)
140 / 232 / 348 (spirit orb)
Max Life1500
Defense 0
KB Resist100%
Immune toAll debuffs
Image Name Condition
Happy Phantom Spirit.png Happy Phantom Spirit Phase 3

Aftermath[edit | edit source]

Notes[edit | edit source]

  • Leaving the Dungeon will cause Polterghast to enrage and despawn shortly afterwards.

Tips[edit | edit source]

  • Clearing out a large area in the Dungeon prior to the fight will greatly help. When expanding, Dungeon Brick Walls Unsafe may help to ensure that the player is always considered to be within the Dungeon, so that Polterghast does not enrage.
  • Polterghast has similar AI to Plantera, which means that movement strategies used during that boss fight may work here as well.
  • Ark of the Elements is a great weapon against its first and second phase, however the weapon becomes very ineffective when it reaches the last phase. At that point, it's recommended to switch to weapons that can deal enormous damage on one hit, such as the Blissful Bombardier.
  • Don't rush too much when fighting its last form. The chaotic activity can easily overwhelm the player if they're careless. Take your time and be careful when dodging.
  • Oddly, the Polterghast is slowed in water, allowing the player to encase a certain area and use the Abyssal Diving Suit to their advantage.

Trivia[edit | edit source]

  • Polterghast's theme is Feral Amalgamation, which is made by the artist DM DOKURO.
    • When the Calamity Music addon mod is disabled and the Calamity base mod enabled, Plantera's theme will play instead.
    • Polterghast’s theme used to be Ruin, a remix of In The Hall Of The Mountain King from The End is Nigh.
  • Before the update which allowed players to fight bosses more freely, it was required to beat Polterghast, as the Ruinous Soul was required to craft the Cosmic Worm.
  • Despite being a boss, it doesn't have a Boss Mask or a Lore item.
  • The boss’ multiple names are the result of a sort argument between the spriter, LordMetarex, and the lead developer, Fabsol, also known as MountainDrew. The spriter was naming his files ‘Necroplasm’ and was using it as the official name for the boss. During a spoiler, the official name was revealed to be ‘Polterghast’. After an argument the developer decided to use ‘Polterghast’ for the first phase and ‘Necroplasm’ for the last phase. ‘Necroghast’, being a combination of the two names, was used for phase two.

Lore[edit | edit source]

Over the course of Yharim's conquest over the world, countless people perished - whether killed by his forces, imprisoned and fed alive to his monsters, or struck down by Yharim himself. Few died peacefully, and many cursed the Jungle Tyrant's name with their last breath. Some found peace in their afterlife; others lingered in the physical realm as phantoms, their hatred and anguish immutable even by death.

The Dungeon served as Yharim's prison during his rule - and for the less fortunate, his torture and execution chambers. Attracted to the bloody reek of pain and death, the restless spirits flocked to the Dungeon in droves, possessing the corpses of the deceased and animating armors and weapons. Though easily dispatched at first, their numbers grew and grew - seemingly without end as the death toll of Yharim’s reign continued to rise. Deeming the Dungeon a waste of his men and resources, he withdrew them and left the dead to rot.

As spirits clinging to reality through little more than hatred, they held no loyalty to their fellow dead. Many swiftly turned on each other - souls devouring souls in an instinctual bid for power. As lesser souls grew swift and elusive, the first souls to feed continued to fight and consume one another until a legion took form, lacking even the concept of predator and prey. Hatred for the one that first slew them and a desire for more that could never be satisfied; reduced from countless living men to a mindless beast, nothing else drove the amalgamation now.

Scraping fragments of metal into patchwork armor and animating broken chains with its essence to better hunt its lesser brethren, the Polterghast roams the depths of the Dungeon away from prying eyes. It continues to feed and fester in the darkness until it feels the power of the object of its collective hatred once more...or until it detects one whose power has begun approaching the point of indistinguishability.