Girolamo Da Lucca was a Master Assassin from Florence, and an expert in melee and stealth during the Renaissance. His background remains a mystery to this day, but it is believed he had strong ties to the Medici family and a personal vendetta against the Borgias of Spain.
He began his career working as an assassin for hire and developed a reputation for his obfuscation and infiltration skills. He would perform mass assassinations, killing twenty men without detection or sign of entry. His deadly talents and his ability to disappear without a trace earned him the title "The Ghost of Florence".
Ezio became aware of his growing reputation and approached him to join the Brotherhood. Girolamo felt an affinity for the Creed and accepted.
When Ezio gave notice of his departure for Spain, Girolamo insisted on traveling with him, possibly to pursue his own agenda.