The Guild of the Torre degli Angeli was an organisation of researchers with its headquarters in the Torre degli Angeli in Cittàgazze. The guild was responsible for the creation of Æsahættr. The people of Cittàgazze, who believed the guild found a way to enter other worlds using a key, a spell or alchemy, blame the Guild for ruining their world by letting in the Spectres. The last bearer of the subtle knife before Will, Giacomo Paradisi, confirms the people's accusations. He admits that the Spectres were let in when the Guild split the "bonds that held the smallest particles of matter together," but isn't sure where the Spectres come from.
Paradisi implies that at the time of the knife's creation the Guild conducted itself with dignity, devising strict rules for the use of the knife. Shaman Stanislaus Grumman says that when the Guild made the subtle knife, they "created a tool for their own undoing." Cittàgazze ceased to produce anything. Instead, "that Guild of thieves," as Cittàgazzean Joachim Lorenzo calls them, simply took what they wanted out of the other worlds the knife allowed them to visit.
What the Guild never realised, according to Grumman, was that the knife could have been used to challenge the Authority: "they invented a device that could split open the very smallest particles of matter, and they used it to steal candy."
- The Subtle Knife (Mentioned only)