Born as an Orphan in the streets of Rome , Quirino, while a skinny boy, showed bravery and rebelliousness since little, he showed quite aptitue to sneak around and never showed fear to height as he used to jump and run on the rooftops to help other orphans when stealing food. In 1498, Cesare Borgia devised a plan to fight the Italian Assassins, to that end he selected four orphan boys, Quirino among them, for their character and abilities and sent them to the Vallombrosa Abbey, while tricking veteran Spanish Assassin Raphael Sánchez into training them as Assassins for the next five years. Once he had determined that their training was complete, he appointed his ally Sirus Favero as the leader of the fledgling group, which he called "the Crows". It would be Sirus that presided over their indoctrination into Templar doctrine. By treating every Crow as his son, and the organization a family, he managed to cultivate the group steadfast loyalty, Quirino the most. Equipped with the Corvix Blades, the Crows were able to emulate the killing techniques of the Assassins, striking their prey from the shadows or under cover. From 1503 to 1506, they exploited these skills not only in their assassination of Cesare's enemies, but also on hapless peasants throughout Tuscany. Despite their status as a covert force, they frequently launched brutal raids against villages and farms, massacring civilians for sheer sport.
Over the years, tensions had escalated between Sirus and Cesare owing to disagreements over ideology and direction of the group. By the time of his capture by the Assassins, Sirus had come to loathe Cesare, who declared that his organization had gone rogue in turn. Sirus entered into Machiavelli's confidence, proving his loyalty by helping the Assassins sabotage the Borgia's plans on numerous occasions, a matter that did not conflict with his goals. All the while, he plotted the day he would take revenge against the Assassins for the death of his son Matteo.
When the duplicity of the team was exposed, around 1506, Merlo led one of the Crow's column in the final assasult, while Sirus fortified himself on the Castel Sant'Angelo, the Assassin however surprised him and his bodyguards and killed all of them. Despite outnumbering the Assassins with an army, the Crows' morale broke and many surrendered, among them Quirinus, who had come to loathe his group for the mass killings and lack of purpuse. Unlike his surviving former crow partners, Merlo choose to flee to Spain, instead of Forli, this would save his life. Merlo abandoned his former life as a Crow, never fighting or performing missions again, and lived the rest of his life peacefully.
Conceived as a counter-Assassin unit of the Templars, the Crows were trained firsthand in the martial arts unique to their adversaries. They were meant to be a shadow organization who, like their enemies, achieved their aims through assassination. For that reason, they mirrored the Assassins' agility and expertise at stealth and evasion. Iconic to the Crows were the Corvix Blades, modified Hidden Blades identified by the head of a crow carved deep into their blades. Aside from this weapon, they wielded exotic swords and were distinguished by their uniforms: jet-black leather armor, decorated with crow feathers and complete with a small cloak. Only the Crow Leaders, like Quirino himself, were entitled to the signature uniform and Corvix Blades.
Merlo's techniques were based on the Spanish Brotherhood clasification system (translated into italian as: Ombra, Esecutore and Specialista). According to this, Quirino was mostly an Ombra type of "Assassin".
Quirino's Genetic Memories is being synchronized by his modern descendant Juan Sokol in order to improve the Argentinian Assassins' Training Program.
- The name Quirino is possibly derived from the Sabine word quiris meaning "spear". Quirinus was a Sabine and Roman god who was later identified with the God of War MARS. Merlo was named after the Martyr Saint Quirino, since he was born on the saint's feast.
- Merlo, means "blackbird" in italian, ultimately from Latin merula. The blackbird is a symbol of a naive person.
- Juan Sokol is a modern descendent of Quirino by his maternal side.