You can open books through atrix (on trial) and Mystery Letter (available in the mall) of the Academy. Books of this profession or other professions can be unlocked and upgraded. After upgrading, you can put it in a book bag to increase the character attributes.

Gan Kun is also an indispensable ability in PK. Gan Kun Can improves players' ability to suppress other classes. With the increase of points, the increase of level will increase or decrease the damage of other professions. It is worth mentioning that there is a small hint here: the skill upgrade of Gankun is the consumption of Gankun points, which can be returned when the experience is reset, but please remember that copper coins will not be returned.