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Currently, there are only two official add-ons for Heroes 5: "Hammers of Fate" and "Tribes of the East." All other "products" ("Throne of the King," "Theory of Power," "Wolfhound") are either unofficial fan-made continuations or pirated versions and have nothing to do with the copyright holders. Therefore, you will not be able to register and play on the official Ubi.com server.