The Great Child is the ghost of Harold Shelburne, and the eighth ghost in the Black Zodiac.
Born to Margaret Shelburne as a result of a rape, Harold was raised in a carnival as an attraction and his mother's protector.
Mainly because Margaret never stopped spoiling him as he grew, he not only weight 136 kg by adulthood, but retained his childlike mindset his entire life to the point that he never got out of diapers!
Because of this, Harold and Margaret were taunted and teased at every turn, despite being clearly mentally handicapped.
One day, the circus workers kidnapped Margaret as a cruel joke on Harold. In a rage-fueled search for his mommy, Harold destroyed most of the carnival, and when he found her, she had suffocated in the bag the workers had kept her in. Enraged, Harold chopped up the circus workers with an axe and put their remains on display for paying customers.
When the carnival broker, Jimbo, found out what Harold had done, he ordered an angry mob to mutilate him beyond comprehension.
Following their deaths, Harold and Margaret's earth-bound spirits were captured by Cyrus to become the Great Child and the Dire Mother.
The two were then moved to the basement of the house.
Dennis encountered the Great Child and the Dire Mother in their containment cube in the basement.
The Great Child and the Dire Mother were either the seventh and eighth, or eighth and ninth ghosts to be released.
Later, a Latin chant caused the Great Child and the Dire Mother, along with the other 10 ghosts, to go to the centre of the machine and power it up.
When the Great Child and the other ghosts were freed from Cyrus's trance, they threw Cyrus into a rotating crest of rings.
When the house exploded, destroying its walls, all twelve ghosts escaped the house and into the woods.