Super Subclass is the third tier of class.

Original Method.

To obtain the Super Subclass you must have not of chosen a standard subclass obtain a Medallion of Courage that is for your class, and you must be at least level 9 Base form (No sub), when these conditions are met you left click the medallion and you will transform into a level 1 Super Subclass.

New Method.

For version 2.91a and beyond. Super Subclasses can be obtained by choosing a standard subclass and then reaching level 9 of that standard subclass, you will receive the ability to Super Sub by clicking on the hero abilities tab (the same way you obtain standard subclass) You can still use the original method to reach Super Subclass.