The Mentor

This Achievement/Trophy?is very time consuming. It requires?you to?lock down every Assassin's Den in Constantinople. You do this by first assaulting the den. once you have gained temporary control, assign a level 10 Assassin.

You then will start the first of 2 Master Assassin missions. Once this mission has been completed, you must train that Assassin to level 15. This will enable you to complete the final Master Assassin mission and lock down that area.

In total, there are 7 dens. But, one den is locked down during the course of the story.