A Wisconsin teen involved in the infamous Slender Man attack pleaded guilty Monday to attempted second-degree homicide, the AP reported. Anissa Weier, 15, and her co-defendant, Morgan Geyser, initially faced a charge of attempted first-degree intentional homicide after repeatedly stabbing a classmate to impress the fictitious horror character named Slender Man. Weier, who pleaded guilty to the second-degree charge, still faces a trial next month focused on her mental health. She could spend three years in a mental hospital rather than ten years in prison if she is found not legally responsible for her crime due to mental illness. Geyser pleaded not guilty by reason of mental disease to the initial attempted homicide charges and reportedly plans to proceed to trial.