Dave Mathers
Dave is mentioned as the source of the ten install discs which Arthur uses to create the minds of the AI Crew for O'Neill Station. The implication is that he is quite happy at working with multiple diverse machine architectures, including highly obscure ones. Also, that he works quickly. Most importantly he is 'a genius at making sane AIs'.
Arthur later appears to be trying to teach himself more about creating AIs by studying (copies of) Dave's discs.
On the other hand he is described as 'mad as a hatter' (though it's unclear what form this madness takes), and would appear to be deeply into occult beliefs about ritual and symbolism. He likely follows a 'hermetic magic' tradition, and may have beliefs about alchemy and the transformative powers of handwavium. At least his surname 'Mathers' is probably assumed, and probably references the 'Golden Dawn'.
Implied is that his AIs have predefined skill sets, even hobbies, and that he likely insists on knowing what their names are to be (or, you'll find he has named them himself). It's also implied that he is known in the Eire, or at least UK, occult scene, and may need to move around for 'professional reasons'. Later he may live, or at least spend some of his time, on the Wiccan Ravenmoon Station.
Dave is a secondary character, though an important resource, and does not (currently) personally appear in any stories.
