Feather

Feathers were markers used by the Assassins to prove that they had successfully assassinated their targets. However, after the fall of the Order, the feather lost its importance.

In the Renaissance, Ezio Auditore da Firenze collected feathers for his younger brother, Petruccio; first as a request from him, and later, in his memory.

High Middle Ages
For the Levantine Assassins in the High Middle Ages, feathers were used to both grant an Assassin permission to kill a target, as well as for them to prove that the assignment had been completed.

After investigations on the target had been completed, Assassins' Bureau leaders would give the chosen Assassin a feather, allowing them to proceed with the actual mission. Upon killing his target, the Assassin would stain the feather with the blood of the slain, and present it to the Bureau leader.

Among Assassins, the phrase having a "feather on one's head" meant a mark of death. For example, an Informant in Damascus once commented that "a feather laid on top of Abu'l Nuqoud's head," implying that the Merchant King was marked for assassination.

Renaissance
"Ezio, look at her. I still can't get her to talk! She spends all day and night in front of those feathers Petruccio used to collect. She can't let him go."

- Claudia Auditore da Firenze, regarding her mother.

As he was sickly and often confined to bed, Petruccio Auditore once asked his brother Ezio to collect feathers for him. Though Ezio asked him what they were for, he only said that it was a secret, which he would reveal in time.

After the murder of Ezio's father and two brothers (Federico and Petruccio), his mother Maria was struck to silence for years. She would only remain praying over Petruccio's feathers in her room in the Villa Auditore, in mourning of her lost child.

Ezio thus sought to collect feathers, both in memory of his brother, and to coax his mother into speaking again. As he traveled across Italy, he gathered and placed any feathers he found into a box in his mother's room.

After Ezio had collected fifty feathers, Mario Auditore spoke with him about what he was doing, suggesting that he should give up in what he believed to be a wasted effort. In an attempt to have Ezio turn his attention to other matters, Mario also let him know that a new weapon, the Condottiero War Hammer, was waiting for him at the Monteriggioni blacksmith.

After collecting one hundred feathers, Ezio's efforts were rewarded. Maria spoke again for the first time in years, thanking Ezio for not giving up on her, and presenting him with the Auditore Cape.

In later years, even after the Fall of Monteriggioni, Ezio would continue to collect feathers in Rome; particularly those found on landmarks throughout the city. He placed these feathers in a chest at the Tiber Island headquarters, which resembled the feather box that had once been kept in Maria's room.

American Revolutionary War
On one instance in 1769, Ratonhnhaké:ton and Kanen'tó:kon gathered feathers from nests in Kanatahséton at the request of the Clan Mother of their village. During the course of the American Revolutionary War, Ratonhnhaké:ton could also collect other feathers in memory of his village.

Modern times
Before the fall of the Assassin Order, an Assassin safehouse disguised as a dry cleaners used photographs of feathers, coupled with the codeword "Rafiq", as proof of identity. However, the Templars, using information from Daniel Cross, used this information to identify the safehouse and launched an assault.

Trivia

 * Due to his death, it was never revealed why Petruccio collected the feathers in the first place; although a line from the novelization suggested that they were meant to be a present for his mother.
 * Collecting all 100 feathers in Assassin's Creed II unlocked the achievement "In Memory of Petruccio." Depositing all of them in the chest unlocked the Auditore Cape.
 * If Ezio placed all 100 feathers at once in Maria's feather chest, the cutscene with Maria occurred before the one with Mario.
 * Proximity to a feather was signalled by a 'shimmering' sound effect identical to the ones heard near treasure chests, Glyphs and Codex pages, as well as the decipher fragments in The Lost Archive.
 * After Sequence 4 in Brotherhood, a map detailing the locations of all the remaining feathers could be bought from any art merchant.
 * Maria's feather chest was an artifact that could be found in modern Monteriggioni by Desmond Miles.
 * In Brotherhood, feathers were easier to find and track by using Eagle Vision and an unlockable map.
 * Collecting the 10 feathers in Assassin's Creed: Brotherhood unlocked the achievement "In Memoriam."
 * In Assassin's Creed III, all feathers were found in the Frontier, and a map detailing their locations could also be bought from General Stores.
 * Collecting all feathers in Assassin's Creed III unlocked the outfit Ratonhnhaké:ton wore before becoming an Assassin.