After the desert content we got with RfR, I was thinking desert-theme-wise from previous games, we're only missing:
- Djinn (humanoid elementals can come with more content of what element they are and fit anywhere)
- Rocs (Giant bird fits anywhere too)
- Manticores (Hard to do them justice as a mount trait, given their power in AOW3 & potentially a bit plain mechanically as just a flying melee unit)
- Sphinx (needs egypt theme)
- Egyptian style deserty Pyramids (No room for a new egypty culture now IMO - Architects build Pyramids, chariots are mount trait, while Mystic/Nomad cover both eastern and deserty themes together.)
Therefore, what about a "Mythical Beast" leader with an Egyptian styled pyramid as a wizard's tower replacement? As a feature, this ruler type could perhaps get mini versions of itself as mounts for heroes (using the player's cosmetic choices), or perhaps as a special "Myth Beast Rider" unit. To me, this dlc would have an Astral (Mythical/mystical beast posing riddles and prophecy), Nature (Giant Beast)and Chaos feel(Mutant beast hybrid, eat your foes)