These are all of the character classes described in the rulebook for The Source. Each class has its own advantages and disadvantages, and is balanced enough to make things somewhat fair, but not enough that the player is drowned by rules. Each of the classes described in this book will have their own page or two in this book. They will describe the advantages and disadvantages of the class.
Making Your Own Class
Don't like any of these classes? You can work with your Narrator to create your own class. For inspiration on this you can use any set of details as a base to work off of. Start with the high level ideas from any other fantasy roleplaying game.
Come Up with a Backstory
If it helps you get into character, come up with a few sentences that describe your character's background, their life story, how they came to join this adventuring party. Who did they know beforehand? What was that relationship like? How did that relationship influence others in the party?
If this sounds like too much effort, feel free to cut this part out and cast it aside.