Rabulias said: There are two different types: Modules and Add-Ons. Add-Ons can be added to existing games, as Nover says. Modules can only be added when creating a new game, and cannot be directly added to an existing game. As a Pro user, you can create a Module-based new game, then use the Transmogrifier to copy elements over to your existing game. I was afraid Transmogrifier was the only option, not the most user friendly (like if I start with Hoard of the DQ then want to continue it in the Tiamat module...)