Sirus Favero (1433 – c. 1506), also known as "Il Corvo", was the Grand Master of the Crows. He founded the unit alongside Cesare Borgia with the goal of eradicating the Assassins through the adoption of their own techniques.
Despite the proven success of the program, Sirus and Cesare came to quarrel with one another over the years, developing a mutual hatred that would eventually cause the Crows to split from their parent organization, the Templars. When his son was killed by the Assassin Lo Sparviero, Sirus swore revenge against all Assassins and became a double agent, earning the trust of the Assassin leader Niccolò Machiavelli, who was unaware of his identity as head of the Crows. He planned to use this infiltration to destroy both the Borgia and the Assassins, but his duplicity was eventually exposed, causing him to launch a final operation in Rome, during which he was killed by none other than Lo Sparviero himself.
Recruitment by Cesare
Between 1488 and 1494, Sirus Favero earned a feared reputation throughout Tuscany for his murder of several nobles in that region. His famed cruelty appealed to the Templar Cesare Borgia, who sought his recruitment. This he effected through Sirus's abduction, upon which Cesare offered mercy in exchange for Sirus's sworn service.
As an agent of Cesare, Sirus recruited countless men into the ranks of the Borgia. Because of his martial prowess, his main role involved training the soldiers of the Borgia armies. His connections allowed his son Matteo to become a captain in Cesare's army, though he managed to keep this fact hidden from Cesare himself.
Founding the Crows
Shortly after the siege of Monteriggioni, the Cesare Borgia and Sirus Favero concocted a scheme to destroy the Assassins by creating a special unit of Templars that mimicked their tactics. To that end, they acquired a group of young men from an orphanage and invited the Spanish Assassin Raphael Sánchez to instruct them in the ways of the Assassins at Vallombrosa. Sánchez, deceived into believing it was the Assassins that hired him, trained them for more than five years in the arts of stealth and assassination.
One summer, when it was determined that their instruction was complete, Sirus burst into Vallombrosa to seize control of the regimen, informing Sánchez that his task was over. While the confused Assassin returned to Spain, Sirus announced to the trainees that their true training was about to commence and proclaimed that from that day forth, they were to be named "the Crows".
Rise of the Crows
Over the next few years, the Crows became indoctrinated into Templar service. Sirus was successful in building rapport with the men, as he convinced them that he regarded each of them as his sons and their organization, a family.
During the years of Borgia dominance in Rome, the Crows were active throughout Italy, serving as covert agents of the Templars. By employing their own variant of the Hidden Blade called the Corvix Blade, which they created from stolen blueprints of the weapon, they were able to replicate the Assassins' techniques. They terrorized Tuscany, ambushing villagers and peasants in the countryside, but their skill with disguises allowed them to largely elude detection by the Assassins.
As the years pressed on, a rift gradually began to form between Cesare and Sirus as their ideologies began to diverge. By 1506, their mutual hatred caused the Crows to split from the Templars, who from then on pronounced them a rogue organization.
Around late 1506, Matteo rallied the Crows and a contingent of Borgia soldiers around the Colosseum in Rome. Sirus was responsible for transporting an immense supply of Corvix Blades and uniforms there, but such a large shipment attracted the attention of the Assassins, who sent one of their agents Lo Sparviero to investigate.
It was while Sirus was conversing with his son at the base of the Colosseum that they were spotted by Lo Sparviero, who was searching for the Crow's leader. As Sirus was not in uniform, the Assassin did not identify him as a Crow, targeting his son instead. Matteo feigned ignorance, hoping to lure Lo Sparviero into an ambush but was ultimately killed at the top of the Colosseum when the trap failed.
With Matteo dead, the Sirus and the Crows broke camp and departed from Rome. Hours later, Sirus was captured by the Assassins on the outskirts of the city. By emphasizing his resentment for Cesare, Sirus was able to hide his affiliation and gain the Assassins' trust. They were convinced that he was a mere weapons merchant hired by Cesare to deliver the Corvix Blades without any true connection to the Crows.
For some time afterwards, Sirus pretended to be a spy for the Assassins, providing valuable intel on Cesare's activities to the Assassin leader Niccolò Machiavelli. To cement Machiavelli's trust, his information was often true—even helpful—for the Assassins on numerous occasions. It was with his assistance that the Assassins were able to decrypt the coded language that Cesare used for his messages, as he gave them his own copy of the decryption device, which Leonardo da Vinci reproduced.
At one point, Sirus directed the Assassins to a bookkeeper in Florence who worked closely with Cesare. Machiavelli had hoped that the ledger run by this bookkeeper would contain information incriminating to Cesare. After Lo Sparviero retrieved it, the Assassins learned that the Crows were led by a Grand Master nicknamed "Il Corvo" and that their hideout was in Rome, from which they plotted an operation involving the nobles of prestigious houses.
With this revelation, Machiavelli insisted that Sirus stay in Florence with him, fearful of the danger the Crows posed to him in Rome and still unaware that his trusted ally was Il Corvo himself. Sirus refused so that he could continue coordinating the Crows' activities directly from their base of operations.
Months later, Sirus advised the Assassins that targeting Borgia messengers who delivered letters to the Crows could provide a lead in their hunt for Il Corvo. Meeting with Lo Sparviero before the Castel Sant'Angelo, he identified one of these Borgia messengers for the Assassin, who killed the man and passed the delivery onto Sirus as requested. It was in the midst of this hand-off that Lo Sparviero became suspicious of Sirus's behavior, particularly when Sirus instructed him to stay hidden while he personally sought out the Crow hideout. He decided to tail him as he left the castle.
Sirus, however, expected the Assassin to disobey and follow him. Like his son before him, he feigned otherwise, intending to lead Lo Sparviero straight into an ambush. As the Assassin arrived at a small alcove, he was attacked by several Crow Leaders from all sides. When it soon became apparent that Lo Sparviero was winning the fight, Sirus bellowed that he would avenge the death of his son with the blood of all Assassins before using his tricks to flee from the scene. Using his skills as Master of the Crows, Sirus was able to escape from Lo Sparviero as the latter chased after him.
Rallying for a final fight
- "My Crows will do to you exactly the same as what you did to my son! You and all your brothers will pay with blood!"
- ―Sirus to Lo Sparviero[src]
During the next few weeks, Sirus, now with his true allegiance exposed, prepared for a climactic fight with the Assassins. Knowing that they were frantically searching for clues to his whereabouts, he decided to mock them by sending many insignificant letters between his Crows, expecting the Assassins to intercept them and decipher using his decoding device. Soon he began to send messages to all his Crows summoning them all to Rome, where he would launch his greatest operation. The Assassins, once again through Lo Sparviero, intercepted one of the letters in Florence and discovered this call to arms.
On the day that Machiavelli arrived in Rome to deal with the threat, Sirus rallied his forces at the Castel Sant'Angelo, having been alerted to the imminent attack. His Crows flooded the streets of Rome while he laid a trap at his hideout, anticipating that the Assassins would strike there. Erstwhile, he had moved swiftly, killing most of Machiavelli's contacts in Rome. Since his plan did not seem to give the Assassins a chance to regroup, Machiavelli decided to make do with only Lo Sparviero at his side. Meanwhile, Sirus awaited in front of the castle surrounded by three bodyguards and with the Ponte Sant'Angelo heavily defended by his Crows. Rather than fighting his way through the bridge as Sirus intended, Lo Sparviero sneaked to the castle by traversing underneath it.
The lone Assassin, seething with hatred, leapt at Sirus's group as soon as he had crossed over to his side. Although his bodyguards outnumbered the Lo Sparviero, they were nonetheless defeated, with Sirus himself being slain right afterwards. In the immediate aftermath of his death, most of the Crows lost all their morale and surrendered. Machiavelli and Lo Sparviero hurried to the Crow hideout to recover what data they could, including letters arguing with Cesare and references to a Crystal Cube. While hunting for the Assassins, Borgia soldiers burned down the hideout.
After the battle, the Crows were dissolved as an organization and were definitively defeated.