Talent tree mastery and effective talent level

Each tree has a mastery value. This value is a multiplier value to calculate effective Talent level. The formula is:

Effective talent level = Raw talent level * Tree mastery

So for an example, Raw talent level of 4 and mastery of 1.4 you will have the effective talent level of:

4 * 1.4 = 5.6

The mastery value can be improved by spending a category point into the tree, or by some equipments.