Subject Three is the main antagonist of the popular Creepypasta The Harbinger Experiment, being an incomprehensively dangerous entity given life through the titular experiment, where Dr. Zimmerman, the protagonist, and their science team try to contact the metaphysical plain.

After reciting a series of chants, Zimmerman somehow transformed an average test subject into this monster, a completely hairless humanoid with a deformed head, horrifically large, black eyes, and arms that dangle down to its knees. Subject Three eventually escapes, ripping everyone apart to the excruciatingly loud and disembodied song "Livin' in the Sunlight, Lovin' in the Moonlight" by Tiny Tim, and the protagonist is the only survivor. He manages to lock Subject Three in the ravaged science facility and tells the tale, before he begins hearing the song again and accepts his fate.

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