Unspeakable Possessor

Unspeakable Possessors (AKA "Servants of Hastur", "Adherent of the Unspeakable Oath") are from August Derleth's "The Return of Hastur".

Description

And certainly they saw the thing that came crying out at us from the sinking ruins behind, the distorted caricature of a human being, with its eyes sunk to invisibility in thick masses of scaly flesh, the thing that flailed its arms bonelessly at us like the appendages of an octopus.
— August Derleth, "The Return of Hastur"

Grotesque octopus-like creatures created from the body of a wizard by Hastur the Unspeakable after the fulfillment of an Unspeakable Promise in exchange for a favor, to fulfill the caster's part of the bargain when the time comes; if the caster is dead when Hastur tries to possess the caster's body, then someone close to the caster will inherit the curse. Once possessed, the caster's flesh takes on a scaly, grey-green cast, as the caster's body begins to transform into a grotesque, bloated parody of the human form, before becoming an Unspeakable Possessor if the caster cannot fight off or destroy the possession until Aldebaran vanishes from the sky, or the sun rises, whichever happens first. If the possessor is not destroyed, then it will reattempt the possession the next time the conditions are right for it to resume its attack.

Associated Mythos Elements

• setting: Hastur Cycle
• tome: The King in Yellow (tome)
• artifact: Yellow Sign
• deity: Hastur ("The Unspeakable", "The King in Yellow")
• location: Carcosa
• spell: Unspeakable Promise (spell)

References

• fiction: August Derleth, "The Return of Hastur"
• Sourcebook: Malleus Monstrorum