Calliope/Caliborn share the same body. Each is "asleep" while the other is "awake", and they have a pair of ankle-shackles of which magically only one can open. They also have disjoint skillsets; due to some kind of brain trauma, Caliborn is incapable of drawing, while Calliope is pretty good: example

Caliborn circumvents this latter restriction by biting off his own leg.