The Mentor's Keeper was a virtual representation of one of Ezio Auditore da Firenze's genetic memories, relived by Desmond Miles in 2012 through the Animus, in which a memory from Altaïr Ibn-La'Ahad was viewed.
Altaïr rode into the besieged town and saved a fellow Assassin.
- Altaïr: Are you hurt?
- Assassin: Broken foot.
Altaïr helped the Assassin up.
- Assassin: What is your name, brother?
- Altaïr: Altaïr. Son of Umar.
- Assassin: Umar... ah yes. He was a fine man who lived as he died. With honor.
Abbas Sofian came running over to Altaïr.
- Abbas: Altaïr! We have been betrayed. The enemy has overrun the castle!
Altaïr kept his attention on the injured Assassin.
- Altaïr: You'll live.
Altaïr turned towards Abbas.
- Altaïr: And Al Mualim? Where is he?
- Abbas: He was inside when the crusaders broke through. We can do nothing for him now.
Altaïr! We must fall back!
- Altaïr: When I close the castle gate, flank the crusaders in the village and drive them into the canyon.
- Abbas: You don't stand a chance!
- Altaïr: Abbas. No mistakes.
Altaïr made his way to the Masyaf gate and was confronted by Haras, whose men were holding Al Mualim.
- Haras: Another step and your Mentor dies.
- Altaïr: You will not leave this place alive, traitor.
- Haras: No. You misunderstand. I am no traitor...
...for I cannot betray those I never truly loved.
- Altaïr: Then you are doubly wretched, for you have been living a lie.
Altaïr began to infiltrate the castle, while Haras killed three Assassin hostages in succession, beginning with Vahid Ahmedi.
- Haras: Now you call on your lapdog to protect you? You disappoint me. Why not share what you have learned with everyone, like a proper Assassin? Why not share with your brothers the true extent of your ambition? Where is your sense of fraternity?
Haras killed Raşit El Zübeydi.
- Haras: Another good man dies, and still you say nothing! I am surprised. You taught me many things Al Mualim, but patience was not one of them. Speak now, or I will cut out your tongue that you may speak no more!
Your time is running out, old man. Tell me what you know of the artifact! Tell me where you are searching for it. It is a small price to pay to preserve what you have built here, no?
Even if you found the artifact, what good would it do you, eh? You have neither the skill nor the breeding to wield its full powers. In your hands it would be a seductive and powerful weapon, yes... but nothing more.
Haras killed Fahd El Fehmi.
- Haras: There now! Three men dead because you refuse to talk. Your silence will be the death of you too, Assassin. My Master wants answers. And if he does not get them, he will gladly take your head!
Altaïr assassinated Haras.
- Haras: You put too much faith in the hearts of men, Altaïr. The Templars know the truth. Humans are weak, base, and petty.
- Altaïr: No. Our Creed is evidence to the contrary.
- Haras: Ah... perhaps I am not wise enough to understand, but I suspect the opposite. That I am too wise to believe such rubbish.
Haras died, following which Altaïr walked with Al Mualim.
- Al Mualim: You offered him a chance to salvage his dignity. Why?
- Altaïr: No man should pass from this world without knowing some kindness.
- Al Mualim: But he shunned your graces.
- Altaïr: As was his right.
- Al Mualim: Altaïr, I have watched you grow from a boy to a man in so short a time, it fills me with as much sadness as pride. You fit your father's shoes as if they had been tailored to your feet.
- Altaïr: I did not know him well as a father. He was an Assassin above all.
- Al Mualim: You too were born into this Order. Do you regret it?
- Altaïr: How can I regret the only life I have ever known?
- Al Mualim: You may find a way, in time. And it will be up to you to choose the path you prefer. Come, my boy... and ready your blade. This battle is not yet won.
Altaïr assassinated Haras and rescued Al Mualim.
- Although the crossbow did not feature in the first Assassin's Creed due to timeline concerns, Haras used it to kill his Assassin hostages. It was also used by ordinary Templar soldiers.
- Altaïr was able to perform certain assassination techniques that were not available in Assassin's Creed, such as the air assassination and ledge assassination. Accompanying this, he was also able to perform the climb leap and fast climb techniques.
- Due to a glitch, after completing the main storyline, Altaïr's facial features took on the appearance seen in A New Regime memory, along with dual Hidden Blades.
- While part of this mission was shown at the Gamescom 2011 demonstration, Altaïr's lines were re-dubbed for the final release, despite the lack of any changes to the script. However, neither Al Mualim nor Haras had their lines re-done.
- The passage leading to Altaïr's library was open during this memory, likely due to an oversight.