Imperial Academy / Library

The academy is a bonus section in the game where you could use Viziers to perform a study session where they'd typically have to study for 3 hours in exchange for gaining Book and Skill XP. The Academy lets you enlist up to six Viziers to learn something and get better on a particular skill / talent, in addition to the Book and Skill XPs they earn.

By default, one slot is available to you but you can also unlock more slots -- which would set you back a couple hundred Gems, but the investment is very much rewarding. It takes around 3 hours for a whole session to finish, and once completed, the vizier you sent will improve on one of his basic skills / talent - and as they improve, so will your Sultan and your overall battle rating. What this means is that you generally make your army stronger every after 3 hours as long as someone is enlisted in the academy trying to learn something (multiplied by the number of slots you've unlocked therein).

It is advisable that you unlock 5 slots as soon as you can in order to maximize the number of items you get every 3 hours. Additionally, you can unlock its "Auto" feature only upon unlocking the 5 slots. In addition to this, you'd want to visit the imperial academy daily as it is among the tasks in your Daily Quests.

Auto Study:

Lets you pick a roster of 5 Viziers -- which you'd normally take to the academy to perform the actual studying as a shortcut command(for 3 hours). In total, you can unlock 10 slots in the academy, but each study group should be comprised of 5 viziers.