In the world of Mutant City Blues, super powers come from a single source, and are well-documented enough to be understood with forensic science and to have been incorporated into legal proceedings. The Quade Diagram, devised by Dr Lucius Quade, maps them all out, and shows their associated defects. It’s this diagram which makes the forensic investigation possible. It also doubles up as a central source of character generation. In MCB, the names your character uses for their powers are the same name you use a player.
The Quade Diagram, and its role in character generation, exists primarily to evoke the particular setting of Mutant City Blues. It conveys the idea that the setting’s mutant powers conform to unvarying, if not yet fully understood, laws of science. The diagram reinforces the concept that all powers share the same origin. It has some game balance effects, making it difficult for a single player to cherry-pick all of the most dramatic abilities, but these are not its primary point. GMs may wish to warn players ahead of time that Mutant City Blues discards the standard super-powered RPG design goal of allowing you to replicate any hero you find in comic books. You’ll find that you can create knock-offs of certain iconic characters but that others are impossible to reproduce.
The driving convention in a default comic book universe is that every character embodies a unique theme and distinctive set of powers. In the Mutant City Blues world, enhanced characters conform to a number of recognizable types, with slight variations in detail. MCB includes the option to create characters without the Quade diagram if you wish.