Rome Assassins Guild

The Assassins Guild in Rome was formed in 1500, and was responsible for the downfall of the Borgia.

Formation
The guild was formed in 1500 by Niccolò Machiavelli, who had moved to Rome to directly confront the Templars in their headquarters. Machiavelli got in contact with Fabio Orsini, who borrowed an unused storeroom on Tiber Island to him, which became the guild's location. Soon after its formation, Ezio Auditore da Firenze moved to Rome as well, after his hometown of Monteriggioni was ambushed by the Borgia; the leading body of the Templars.

Source

 * Assassin's Creed: Brotherhood
 * Assassin's Creed: Brotherhood'' novel