The skill tree is found in the top right of the screen, next to the Inventory and Skill Book buttons above the minimap. Alternatively, it can be accessed by pressing the "N" button.

There are three skill trees:

Within each tree are three dedicated branches, each offering a different boost to the class. Players are free to choose skills across the branches or may specialize in one. Each point devoted to a branch will increase the mastery associated with that branch.

Skills can be learned by left-clicking and unlearned by right-clicking. The entire tree may also be completely reset.