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I always thought of the Sylvan faction as Celts, but there's a lot mixed in there.
But personally, I think you can't just focus on a specific culture; you have to start with the world and make the faction look harmonious.
Egypt is close to the Academy; many types of beastmen are named after Egyptian gods, and in the documentation, there were Taurts (human-hippos) and human-jackals, although not in the style of Anubis.
In Elemental Guardians, it's already gone a bit overboard – Anubis appeared, and there are human-eagles with and without wings.
And the Sphinx is a construct from the Shantiarian civilization; mages sometimes use them, but not on a large scale.
Added 7 minutes later
But here again, you need to separate what is living Egypt and what is Necropolis.
In Heroes 6, the Necropolis tries to appear as something Sumerian – there's a Namtaru and a Lamassu, but in reality, it's just a strange Egypt – they live in pyramids, have their own version of the Sphinx, and all the vampires and liches are wrapped in bandages under armor like mummies.