Vivaldi is an outcast wizard, a former member of House Verditius. He was Wizard Marched out when the Quaesitores found him guilty of dealing with demons, but he managed to elude their pusuit. Vivaldi's specialty is in creating toys, specifically marionettes. In creating some of these small automatons, a demon took interest in them and investing them with infernal spirits. He entered an agreement with Vivaldi to get him vis and more magical knowledge.
Now his marionettes steal vis and valuables as he himself travels as a humble toymaker. He is clever and has made at least two realistic, full-sized automatons of himself to throw off hunting Hoplites. More may exist to help him escape justice.