Dark Mountain was originally one of my older scenarios which can be found in the 10-map compendium submitted by me to the miscellaneous section (because it couldn't exactly be considered as a scenario upload) and was meant originally to be a balanced map strictly for 2-headed giant maging (small arena with lots of mana and spells over C.H. C.) The original can still be found in the archives.
What I have done with the scenario was to keep the underground section with some new additions mostly intact, and change the whole scenario so that it now is sort of an epic scenario, but with 2 different ways to win: team one (Karissa & Meandor) find themselves surrounded with mines and ruins to plunder/rebuild, while team 2 (Skulkan & Nekron) don't have many cash resources, but they have massive amounts of mana from chaos rifts as well as building resources and catalysts, favouring spell growth (build magic structures, gain casting/research points) for near-instant build. So far, while I have sort of mastered the way of "assymetrical balance" in my maps, I still haven't been able to create "traitor players" and/or "tag team" games. Nonetheless cash will create lots of standard troops, while catalysts and mana will generate tons of spells and god-knows-what...
I strongly suggest that players use the original spheres and races assigned to each wizard.
The scenario also contains quite a nifty little quest for those who hate swimming. I'd love to say what it was, but I don't wanna spoil the fun for my fans out there :P
Nice areas, some are truly inspiring and never seen before!
Word of caution: Be careful with the elevation trick that you have used. It often looks nice but it can compromise playability and it can even cause bugs (units being unselectable) if they are too steep.
I wouldn't use this map in multiplayer for that reason, for example. Check out my Drums of Death-map for a solution to this problem (it's scripting a change terrain event in the missing hexagons).