NHF – new heroes for Heroes V 3.1.

Why do all the mages have Duncan's medallions? Is it some kind of order?

I'll tell you more, they not only have the medallion, but everything is Duncan's:)
Don't you want to create a new model with animation for each character?
You see, there's already a lot of stuff hanging on them, there's just no room for a medallion... And simply replacing the texture won't give anything remarkable; it's small, and there's not much room to work with. Most of the texture is the antlers of a deer. There's only the face left for creativity, but I tried drawing a crystal, for example, a ruby, and it's simply not visible on the model. So, let's leave everything as it is.
And there's no guarantee that if we introduce a new model of this "medallion," it won't disappear later. It's also important to attach it properly, as Duncan's chest is animated; he breathes, and this "medallion" might simply disappear periodically...