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Two 13-year-old-girls accused of brutally stabbing a classmate to please make-believe horror character "Slender Man" will be charged as adults, a Wisconsin judge ruled on Monday.

The girls are each facing one count of attempted first-degree homicide, where they could face up to 65 years in prison if convicted as adults, according to the Associated Press. In the juvenile court system, the girls would only have been held for five years, until they turned 18.

NBC affiliate WTMJ reported Monday that the girls' attorneys said trying their clients in adult court would be cruel and unusual punishment, and argued that the teens would get better mental health treatment in the juvenile system.

The two Waukesha teens are accused of luring their friend to the woods in May 2014 where she was repeatedly stabbed in an effort to please the fictional online ghoul Slender Man.

According to interrogation tapes released by Waukesha Police, the two girls said they believed the Internet character could hurt them or their families if they didn’t carry out the attack.

All three girls were 12-years-old at the time of the attack, in which the victim was stabbed 19 times but lived.

NBC News is not currently naming the suspects in case the trials are moved back to juvenile court, where proceedings are closed to the public.