In the Year of Four Emperors, magic has risen to a new level of prominence, with each of the contenders for the imperial throne mustering magical forces to help solidify his claim. 

I've also started adding some more mythic elements to the world story, like the idea that tieflings are descended from the Hyksos (who made a bargain with Baal and/or Set to claim rulership over Egypt) and dragonborn from the god-dragons of Mesopotamia. 

What are other fantastic elements worth considering to add a level of fantasy to this world?

  • What are the titans? (Empyrean, Kraken, Tarrasque=Apophis?) They don't share a common origin or nature; they're near-divine beings that exist in the mortal world. In addition to these, the Elder Dragons of Mesopotamia are dragon titans. Krakens and other monstrous titans (a hydra titan?) might be offspring of Echidna, the Mother of Monsters. Who might be a titan herself, or a demon lord.
  • What about demon princes and the hierarchy of hell? Planar cosmology? A metamyth? What's the story that explains how all these gods and pantheons relate to each other and the world? 
  • Other dragons in the world besides the Mesopotamian gods?
  • What does syncretism represent in the actual divine world? Does Serapis exist apart from Osiris? Is there one Isis or two? Do dead emperors actually become gods? Or is there a single pantheon of gods who are worshiped under different names by different people? (And what the heck am I saying if I include YHWH in that?) 
  • Or maybe the actual gods are unknown and unknowable, human faith the only material thing, and godlike beings like titans, demons and devils and angels, and dragons the only mythological creatures that interact with mortals. And they exist in a spirit world that is closer to the material Plane than the outer planes. That fits surprisingly well with Neoplatonic philosophy.
  • Genies are important figures in Arabia, North Africa, and possibly Persia.