Reiter
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Is that the Azure Dragon? Why is it a campaign unit? Well, I think dragons should be ranked like this: Mythical - 8 LV, Rusty and Crystal - 9 LV, Azure - 10.
The Dragon is a powerful unit with the Wizard specialization, capable of transforming Mages, Archmages, Monks, and Fanatics into Wizards. It is indeed from the "Dragon Slayer" campaign and is simply prohibited on regular maps.