If they remain on the surface for over 10 seconds, Polterghast will accelerate away and despawn.

If the player travels to the Surface, Polterghast will enrage, gaining a speed boost until they return. Its projectiles' speed and rate of fire are also affected by these boosts. If the arena is smaller it will move slower, and if the arena is larger it will move faster, proportional to the lack of blocks. Polterghast will receive a boost to its speed depending on the size of the arena it is fought in, which is determined by the amount of active tiles in an area around it. In the second phase, however, these appendages will detach and begin firing projectiles independently, before re-attaching in the final phase as Polterghast summons an unbound clone of itself.

Polterghast behaves similarly to Plantera, chasing the player quickly while using four long appendages to grapple blocks. After defeating it once, using a Necroplasmic Beacon becomes the only way to summon the boss. 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.

Polterghast can be summoned by using a Necroplasmic Beacon in the Dungeon.

Darkest dungeon treating affliction