When Riccardo Belli was younger, he attempted to create life as Lorenzo Belli had, using a dog's placenta as a base; however, Debilitas turned out to be a failed creation. He has abnormally large, round eyes. One of his duties involves finding and trapping animals for Riccardo.
He has the approximate mental capacity of a young child, and is prone to outbursts and tantrums. He can only comprehend simple language, and is only heard speaking short, garbled phrases: "My dolly", "Out of my way!", "Where is you?!", "Fiona! Fiona!" and the rarely heard "My little poogly pie!", "Good smell!", and "Me mad!" (occurs if Fiona hides at the evasion point after pushing the bookcase on Debilitas).
Because he is part dog, he has a habit of sniffing Fiona and sometimes will drop on all fours.
Debilitas adores dolls, and believes that Fiona is also a doll for him to play with, thus he is compelled to pursue her. 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. At one point in the game, Fiona may throw a doll at him, and he falls to the floor in horror as if he believes his doll is injured, possibly meaning Debilitas believes his dolls are sentient beings.
Prior to the game, Debilitas captured Hewie. He harasses Fiona and Hewie for quite a while until all three of them enter the Chapel where Fiona is forced to fight him. The battle has two outcomes: Fiona can either drop a large chandelier on top of him (this does not kill him) by luring him into two objects on the left and right sides of the room, or she can wear his health down until he falls dead on the floor.
If Fiona allows him to live, he will show his true personality as an innocent child, naive to what he has put Fiona through. Debilitas begins seeing Fiona as a holy figure when he sees her silhouetted against the light and stained glass windows of the chapel and will thus interrupt his pursuing, rendering him no longer a threat to Fiona. Fiona sympathetically comments, "Those big eyes... He almost looks like a child of sorts. The size of a giant and the mind of a child... You should be pitied, not hated. I guess I shouldn't have reacted as I did..."
He can also be visited later in his shack, where he gives her the key to the locked stall in the bathroom. The room contains boots and the key to the gate, allowing the player to obtain Ending C if they wish, although the player can continue the game normally.
If the player obtains Ending A, Debilitas appears to Fiona before she leaves the castle. He bows in her presence and treats her with respect. Debilitas looks at the overgrown trees in the garden and begins clipping them as he hums to himself, a possible Scissorman reference.
Debilitas often appears when the player has completed a puzzle or triggered a cutscene. During the first parts of the game, if Fiona deals enough damage to Debilitas, he will run away in pain. However, after picking the lunar refractor, Debilitas will become aggressive.
Debilitas is persistent and powerful but can be easily outwitted by Fiona. He can easily kill Fiona by crushing her in a massive bear-hug and can beat her to death if she's fallen in panic. The player must also be careful when climbing down ladders or else Debilitas will hit Fiona, causing her to fall down and be injured.
Debilitas will rarely find Fiona if she's hiding in a wardrobe or under a bed. However, if she's hiding behind an opened door, his hands may fly through the doors due to a glitch, resulting in Fiona being noticed. As such, if the player chooses to hide behind a door, it is recommended to not hide too close to it.
Debilitas is Latin for "weakness". His name is likely a reference to his "weak" mental capacity.
- "My dolly"
- "Out of my way!"
- "Where is you?!"
- "Fiona! Fiona!"
- "My little poogly pie!"
- "Good smell!"
- "Me mad!"
- Fiona makes a cameo in Joe the Condor's ending in Tatsunoko vs. Capcom, along with Fiona and Hewie.
- His area theme is "Twisted Eyes", stalker theme is "Innocent Freak" and boss theme is "Last Debilitas".
- Debilitas may be afraid of Daniella. When Daniella is cooking in the kitchen, Debilitas will not appear, no matter how much noise Fiona makes or time that passes. The music may stop playing, but he never shows up. This might also be due to the developers unsure of what should happen if Daniella saw Fiona being chased by Debilitas. Debilitas and Daniella are never seen together in the entire game so their relationship is unknown.
- As with Daniella, if Debilitas is killed in "Hard Mode" his clothing reverts to the clothes worn in "Standard Mode".
- It is unknown what Debilitas does to Fiona if he kills her. Some fans speculate that he rapes Fiona, but this seems unlikely considering how childish he is. It can be speculated that he eats Fiona, plays with her corpse, or rips her body open.