Where can I buy multiple heros?
There is a shop in the woods near the back of your town that looks like an Alter of Heros. There is a clearly marked path leading to it and you buy a hero like you buy an Item or a Mercenary from the alter (Move a hero up to it and buy the footmen). This will give you a Rising Champion unit in the hero selection area that you started in and you can then select and additional hero. However due to balancing issues you cannot get the same type of hero twice.
