Simulacra

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The autopsy of the Silly Putty man.

The Simulacra are a humanoid xenos species with slender, pink, fleshy bodies, bulbous forearms and lower legs, and a pointed, featureless head. Simulacra can take on the form of another being for a limited time after consuming that creature's brain. This effect allows them to behave as that individual for the duration of their transformation, knowing everything their prey knew. They're essentially doppelgangers IN SPACE!!! And yes, they are ANOTHER shapeshifting alien. Because GW.

Fantasy

Simulacra are statues made in the image of death gods, ghastly frightening warriors, and various other horrifying beings to guard to the barrows & burial mounds of ancient kings. With the world of Warhammer Fantasy being what it is, these statues slowly become contaminated with death energies from the amethyst wind of magic, Shyish. Slowly the statues are transformed into unthinking but deadly undead automatons that protect the tombs of the dead. These statues were eventually found and tamed by Ole'Heiny and used in his armies and in the invasion of Athel Loren.