A few new creatures are introduced in The Infernal City.
Sea-Drakes are immense fish found in the sea around Black Marsh. They are described as being "like a crocodile, but with paddles instead of legs".
Shearteeth are a type of fish found in the Sump on Umbriel. They have a "maw full of teeth", they can reach at least fifteen feet long, have a long long whip-like tail, dual swimming fins on the underside, "teeth would shame a shark", and a tough hide. They are usually non-aggressive but will attack someone if the sump considers them a threat. It appears that a rare alchemy ingredient called "Sheartooth Loin" is harvested by Skraw for the kitchens of Umbriel, as Annaïg received some (amongst other things) from a Skraw working for Glim.
Hobs are hairless monkey-like creatures used as an assistant to the chefs on Umbriel. They have long arms and legs, very long, thin, delicate fingers, a huge toothless mouth, large green eyes and very simple language skills. Annaïg names her first Hob "Luc" and her second "Dimple".
Wisperills are luminescent films which float through the air in the realm of the Hist. They perform slow, colorful, aerial dances in the air. They were named by Mere-Glim and Fhena when Umbriel is brought to the realm.
- Scamps are also featured in the novel.