The Grotesquery is part of a Faceless One and was believed to be capable of opening the portal for them to come back every lunar eclipse. However, at the end of Playing With Fire, it is revealed by Batu that he had never intended for the Grotesquery to open the portal, instead explaining to Jason Gallow that their gods had been lost in the multiverse for millenia, but that the death cry of the Grotesquery now called them home. This is confirmed in The Faceless Ones, when psychic Finbar Wrong exclaimed that the Faceless Ones had found the way and were waiting at the gate to be let in. The Grotesquery is made of several creatures, including the torso of a Faceless One. It appears in Playing With Fire and The Faceless Ones. The Grotesquery appears to have some form of intelligence as after escaping from Kenspeckle Grouse's hospital, it immediately seeks out Baron Vengeous. It may also have an understanding of human speech, as it only kills Kenspeckle Grouse's assistants when Kenspeckle tells them to fetch nearby Cleavers to ensure the Grotesquery is dead. (Or it may just be for dramatic effect on Derek Landy's part)
The Grotesquery plays a large role in the second novel, Playing With Fire, in which Baron Vengeous and his force of Vampires work to resurrect the Grotesquery and return the Faceless Ones to the Earth. To do so, they need blood with a certain type of power in it, one possible type being the blood of an Ancient, which is what was used to resurrect it. They used the blood of Valkyrie Cain, who is descended from the Ancients. They brought it back with the armour of Lord Vile and Valkyrie's Ancient blood. It increasingly grows stronger and heals faster until it cannot be harmed at all, so the Council lead an attack on it. It wounds Skulduggery Pleasant and Tanith Low as well as killing two hospital helpers, several Cleavers and severely wounds the Torment before it was killed by Valkyrie Cain. It was then mostly cremated by Mr. Bliss, and the torso was kept at the Respitory at the Sanctuary because it could not be destroyed as it was part of a Faceless One.
The Grotesquery's torso returned in the third book as the Isthmus Anchor, which has a connection over the portal to the Faceless Ones. The Diablerie stole it from The Irish Sanctuary (from the Repository) and later kidnapped Fletcher. With the two, they opened up the portal for the Faceless Ones to return, and three come through. After the third Faceless One was knocked back into the other dimension, Skulduggery threw the torso into the portal. The Grotesquery has not appeared since.
It is about the size of two men. Its torso is a Faceless One's torso and the Grotesquery's connection to the The Faceless Ones' universe and also has the heart of the Cu na Gealaí Duibhe. Its right arm is red and fleshy and can fold out and extend to a degree. On its left arm it has a large poisonous spike, which is lethal, and a pus-filled boil that shoots a concentrated acid-like toxin. It also has the ability to teleport, due to the piece of Shibbach that Baron Vengeous grafted onto its flesh. It is not known where this piece is located, or what its limitations are. It has bandages wrapped around most of its body and completely around its face. It bleeds black blood.