Heroes 6 - Discussion

In short:
The Empire worships Elrath (Light), the Tower – Malassa (Darkness), the Stronghold – Silanna (Earth), the Naga – Shalassa (Water), the Dwarves – Arkat (Fire), the Castle – Illat (Air), the Necropolis – Ashah (Primordial), and the Inferno – Urgash (Primordial).
No one knows about the Orcs and Wizards, but…
The Orcs will have full-fledged mages – it’s been promised, supposedly… There’s even a hint in the description of the Jaguar Warriors.

Jaguar Warriors often serve as the honored guard of Orcish chieftains and shamans.

However, it’s worth considering whether this should be taken seriously.
The Orcs worship the Father-Sky and the Mother-Earth.
The Seventh Dragon can be considered a dragon mage. They believe that everyone is capable of following his path and becoming a Dragon (i.e., a God). For them, the Seventh Dragon is an example to follow.

The Necropolis has Earth magic, at least, as this was mentioned in the description.

By the way, the Empire will favor Light magic, and the Inferno and Necropolis will favor Primordial magic. This was confirmed by one of the insiders. Whether to believe it or not, I don’t know.