I've played this one several times and quite like it, but it could use some improvement. I cheated significantly when playing as the Doviello and Hippus, but have played as Auric more often, once without any cheating. (Once I only cheated to deal with Minister Koun. He had split of from Tasunke and controlled the territory of the Pass itself, and could not be convinced to let us pass though his territory. Since the permanent war and peace option is set in this scenario, there wasn't much I could do.)
The scenario seems slightly too easy, imho. The Pristin(us) Pass seems to easy to find. I'd rather there be a longer, winding path though the mountains with some false leads, more Guardians, and more of an enemy presence between you and the Pass. I think it would be better if most of the enemies' cities were on the same side of the mountain as you. In fact, it seems a little odd that these empires could have settled in the storage place of the gods at all. I'm tempted to say that there should be nothing north of the mountains than a wasteland, The Dragon Bones, 3 live dragons, and maybe some other beasts like Gurid and Margalard. (I also tend to think that the dragons themselves should be much stronger, at least having Blitz.)
At first I thought that the portals were really cool, but they annoy me now. I find the need to cast the enter portal spell an annoying bit of micromanagement. At the very least it needs to be <bIgnoreHasCasted>1 instead of <bHasCasted>1. I think it would be much better to instead have a <PythonOnMove> call that transports any unit that moves there to the proper exit. Also, the Portal graphics really don't fit the decor of a mountain pass. It isn't like you are supposed to be teleporting though another dimension, just going underground. I think they should be changed to just look like a stone archway like in AoI or a doorway like in the dungeon portion.
The Hippus seem very strong in this scenario. They can quickly overrun the Barbarian and Kuriotates cities south of the mountains to develop a large and thriving empire and have a good research rate.
The Doviello are weak. Like in the main game, they need to expand early to do well, but they are in no position to expand. They've never actually been defeated in my games because of help from the Illians and Hippus, but they only really expand by having cities gifted to them and they tend to stagnate. They can barely defend themselves from the Sheaim, much less take over them like the Hippus do the Kuriotates. I (as Auric) also end up having to build most of the improvements in the Doviello lands. The Hippus capture several workers from the barbarians and Kuriotates, while the Doviello have to build their own and loose several to the Sheaim.
Things might work better if the Doviello and Hippus (or Kuriotates and Sheaim) switched places.
The Illian capital seems like it is in a bad spot to me. I despise having cities 1 tile away from a river. It was enough to make me learn how to edit scenarios in notepad to move the city 1 tile to the west.
(While I was at it, I also decided to place the Auric unit in the game. I'm surprised we haven't seen more of him in the scenarios. It seems to me that all the Auric scenarios should include the unit and require you keep him alive. I then decided to make it so that when Auric reaches the Dragon's Bones he destroys the improvement and brings Drifa back to life. I'm considering making Tasunke be a vassal instead of a permanent ally and having his loose his traits and declare war on you when raise Drifa, to fit with the story revealed at the end. I was also thinking that bringing Auric to Drifa's bones would be a good victory condition, but then I realized that this would make it just about impossible to win if the human was playing as the Hippus or Doviello.)