Changing Themes
Although a theme can last throughout your character's career, circumstances might arise in which it makes sense for your theme to change. You could begin your career as a watershaper and later find yourself working for Zaaman Rul, a fiery primordial. You might then abandon the watershaper theme and adopt firecrafter, especially if Zaaman Rul replaces your previous patron.
When you can retrain, you can exchange your theme for another instead of using any other option for retraining. To retrain a theme, however, you must have none of the theme's optional powers, and you must have neither feats nor a paragon path for which the theme is a prerequisite. A paragon path that requires your current theme prevents you from retraining that theme, since paragon paths can't be retrained. But if you have only optional powers or feats that prevent you from retraining your current theme, you can retrain those powers or feats to others that don't require your current theme. Once you have retrained all character elements that require your current theme, you can then retrain your theme at your next retraining opportunity.