An artificial lifeform known as a homunculus.
He was completed by Riccardo when he was young and what happened with failed clones was uncertain, under the guidance of Lorenzo, while he was still in training, before the decisive cracks appeared between Lorenzo and Riccardo. However, due to his technical inexperience, he turned out a malformed failure.
Afterwards, Riccardo honed his skills and learned how to create homunculi more like human beings, but upon learning that he himself was incomplete he formed a dislike of complete homunculi, one day disposing of all of them, leaving only the failures like Debilitas.
Perhaps due to the fact that he was created using a dog's placenta as a base, he has abnormally large, round eyes, unbefitting of such a giant. They are not cute, though, and coupled with his unnaturally stiff face they are nothing but disconcerting.
He is intelligent enough to understand orders and respond, but his vocal cords are undeveloped and he cannot talk normally. He performs general tasks around the castle, such as gardening. It was Debilitas, under the orders of Riccardo, who captured Hewie.
He worships the goddess statue in the chapel in his own way, creating an altar in his shack and enshrining dolls he gathers, having a pure mind unsuited to his appearance.
When he corners Fiona in the chapel, too, he looks up at Fiona almost seeming to pray, thinking of her like the goddess statue, becoming then to Debilitas someone that he must not touch.