Story: Altaïr made use of his sword throughout most of his early life as an Assassin, using it with great skill and ease during missions such as the quest for the Chalice.
By 1191, he instead began making use of a Syrian sword with a curved blade and a golden hilt. However, this sword was taken from him after Al Mualim demoted him to the rank of novice for breaking all three tenets of the Creed.
During his progression back into the higher ranks, Altaïr started off with a basic sword similar to his personal one, though it lacked a cross guard. After he assassinated the first four of his nine assigned targets, another sword, this time with the cross guard shaped like an eagle's wings, was granted to him until finally, upon the 7th target, his personal sword was returned to him. The leather grip instead was replaced with a silver and light grey color with a tribal design. He made use of it until the Syrian sword was granted to him again.
Ezio Auditore was able to purchase Altaïr's sword from the blacksmith of Monteriggioni for a large sum of money, and made use of it when he fought Rodrigo Borgia in the Sistine Chapel.
He continued to use it as he escaped the Vatican with his uncle Mario. During the Borgia's attack on Monteriggioni, however, he did not have time to re-equip it, resulting in its loss in the rubble of the Villa, along with Altair's armor and Ezio's other weapons.
Some time after establishing his Assassins Guild in Rome, he was able to recover the sword again after completing all five Assassin's Guild challenges, and he made use of it during the siege of Viana.
Though it is unknown what happened to the sword during Ezio's travels to Masyaf and Constantinople, he only began using it again some time after allying himself with the Ottoman Assassins, after completing the third series of the Assassin's Guild Challenges.