Ectoplasm is a mob added by Harken Scythe that looks very much like a green slime that is created when a Soul Crucible filled with souls is destroyed. The amount of souls that were in the crucible corresponds with the size of the Ectoplasm.
You may right-click the Ectoplasm with an empty Essence Keeper or an Essence Vessel to fill it with souls. This splits the Ectoplasm into smaller slimes until it disappears, and the Keeper/Vessel will then have the same amount of souls that the crucible originally had.
One should also be aware that if they kill a spectral miner. Several ectoplasms will spawn where it was killed.
Ectoplasms can be distinguished from normal slimes by their contracting animation; in the above picture, it is at full compression. This is similar to the Magma Cube's spring-like behavior.
It is hostile and will attack the player.
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