This character only appears in an Explicarium. They are not mentioned nor appear in the main story.
Phradius Bonaventure is an elephantine who is presumably from Brandenbrass. He is mentioned in an announcement in the copy of the Defamière in which Europe is accused of being a sedorner. In the announcement, Bonaventure insults Madigan and declares that he is glad to be relieved of her attentions.