The organization was originally created by orphans who had lost their parents to the Black Plague.
New members are recruited in the form of orphans kidnapped by members of the organization throughout Europe. The children are thrown into a dungeon together and denied food. Eventually, when at least one child has died of starvation, food is provided for the others. Eventually, the children come to realize that the death of one of their own allows them to eat and survive. The end result is one surviving orphan, who becomes a Bird of Passage member.
Members were placed into three units who were in charge of handling different parts of the assignment. The first unit was in charge of gathering information. The second unit handled the extermination of the 'VIP' (main target). The third and final unit were in charge of 'clean-up' and elimination of any witnesses or escorts. The third unit's task was considered the most dangerous of them all. Tira was a member of the third unit.
A characteristic of kills made by Bird of Passage members is to disfigure the body after death. Due to their unique methods and fighting styles, the marks left are quite distinct, letting their clients know the assassination was their doing. This scarring of the bodies of their targets was known as a 'Sky Burial'.
The Bird of Passage was seemingly destroyed on the night the Evil Seed was released, as the blitzkrieg disintegrated the minds of the chain of command. Tira was freed from captivity during this catastrophe, which took place during an assignment.
24 years later, an incident occurred at Kaunas in the Polish-Lithuanian Commonwealth. A nobleman's son was murdered, his corpse horribly disfigured. His servant, turned fiancé, was imprisoned for the murder. However, she vanished from her cell and the rest of the man's family was murdered shortly thereafter. Due to the similarities of the murders to the 'Sky Burial' method and the quick escape of the sole suspect, many believed that the woman was a member of the Bird of Passage and that the organization had assisted in her escape after her capture. This 'Kaunas Sky Burial' incident led to the name "Bird of Passage" becoming well known throughout the country.
Ring blades were the weapons favored by the assassins of the Bird of Passage, and were exclusive to no other organization. The Dance of Death, the battle style used to wield the ring blades, was perfected to both efficiently slay the target and to reveal exactly who committed the deed. Although the Bird of Passage was concealed in the shadows, each killing sent a clear and unequivocal message. The Dance of Death's purpose was to mesmerize and bewilder the victim beyond any hope of retaliation and then swiftly cut down the victim.