Transformation Wizard Avant-Garde:
A great deal of soul energy is needed to transfer subclass powers to the main class. Although you vanquished the Bridle of Soul by Mimir's Elixir, it is not so easy to practice it.
To utilize the subclass power, you must be ritually cleansed by both the Dark Wizard and Mimir's Elixir. Visit the Dark Wizard inside the Dragon Valley to obtain the magic power of transformation.
Once you have learned the magic power of transformation, visit a subclass master in order to certify your ability. Then come back to me on your main class.