Brother Gamon is the High Brother in charge of the department that does divination, through a variety of magical and semi-magical means including scrying, astronomy, and card reading.
When Earth invader Sandra happens to walk into Calculus Horn, she is there because the Brothers of that department have been charged with creating horoscopes for all the visitors, and have decided to start with Sandra because she resembles a member of the fearsome and talented Azandi people of their world, who are respected for their unique magical talents.
Sandra (who is not averse to a little extra respect) decides, when she hears that they do card readings, that she can mess up their Tarot approaches something fierce by inventing ways to lay out the cards that have no meaning or significance. The Brothers in that department, and especially Brother Gamon, are fascinated by the tales she spins them, and even more fascinated by Sandra. Thus she pursues her group's mission in her own special way.