The infernal city was written by Greg Keyes and published in 2009. It is one out of two novels Keyes has written, based upon the story of the 2006 video game The Elder Scrolls IV: Oblivion.
Four decades after the Oblivion Crisis, an unknown mass appeared on the coast of Black Marsh during a powerful storm. Meanwhile, a Dunmer assassin named Sul awakens from a nightmare in which he and Colin, a young Inspector for the Penitus Oculatus, inspected the area where Attrebus was attacked. He discovered a decapitated and charred body with Attrebus’ Imperial signet ring, but thought it was too convenient to be authentic. Meanwhile, Attrebus awoke tied up and riding a horse.
During the attack, Annaïg lost the locket that connected her to Coo, but accidentally acquired Qijne’s invisible, possibly biological, blade, which wrapped itself around her forearm and extended as she wished. In an outdoor area of Umbriel that Glim discovered called the Fringe Gyre, he found trees that appeared to be related to Hist, since he could hear them murmuring.
They traveled to Water’s Edge for supplies, and while there Attrebus tried to garner support from an old friend, Captain Florius Larsus. Florius agreed to join Attrebus, but while waiting for him in a tavern Attrebus was attacked by a group of people hired by the same that hired Radhasa and her allies to kill him. He found that one of the men that attacked him worked for Florius and ran back to find him sitting at a table, a knife wound in the base of his skull.
Glim and Annaïg back on Umbriel, defeated. They spent a few hours together before saying their goodbyes, and Annaïg headed back to the kitchen. She promised Glim that, while all they could do was continue to move forward, eventually they would be free. She then resolved to become stronger and more ambitious in order to survive.
The infernal city is very good if you have some sort of knowledge about the game and/or the lore. I’m sure you could enjoy it without the prior knowledge too but i imagine some things would not make a lot of sense. Either way, i would recommend the novel, it was a great read.