Hasan Pasha
 
Hasan Pasha was a high ranking Templar during the early 1500s and a close confidant to Prince Ahmet.[1]
Biography
A short time after the 'Little Judgment Day' and after the failed attack on the Assassin Headquarters in Galata Hasan recieved a letter from Prince Ahmet telling him about the Prince's uncle Cem, who he says, started the Ottoman and Byzantine Templar goal
In the same letter, Ahmet told Hasan of Polo's Journal and what it contains. He then further instructed Hasan to 'scour' the tunnels beneath the Topkapi Palace.
Soon after finding the Memory Seal, Ahmet futher spoke to Hasan, about Cem's goals and his dealings with the Borgia. Ahmet also confided in Hasan that Manuel Palaiogos has sent him an invitation to meet him, and that Manuel claimed it was he who was resposible for the influx of Mercenaries in Constantiople. Ahmet told Hasan, that while he could not call Manuel a friend nor could he trust him, Manuel was an associate of Cem and and that they 'must let such a monumental mistrust lead to the misfortunes that befell' Cem, and that Ahmet and Manuel together could unite the West and East (referring to Christains and Muslims) worlds into one Empire.
And gave Hasan instructions to arrange a meeting with Manuel. While on his way to meet with Manuel, Hasan was attacked by the Assassins, but came away the victor.
Hasan attented the meeting between Ahmet and Manuel, and claimed that they seemed an unlikely pair, but that they has grown to 'trust each other in the past few days', and that each established their roles; Ahmet woudl search for the Memory Seals, while Manuel trained new Templars using established bases in Rhodes, Derinkuyu and northern Thrace.
Hasan was with Ahmet when the latter asked Manuel to tell him more about Cem, and so heard Cem's story firsthand. However the conversation was cut short when a detachment of Selim's men found them. Hasan took a role in rallying the defenders and successfully beating the detactment.
References
Assassin's Creed: Recollection