Just beat the game via the master quest vs 8 normal and 1 Ridiculous AI. Here's the problem: there is a research requirement for it that I never fulfilled. I had a ridiculously high lvl Sovereign + 3 Ashwhatever Dragons from the Dragon Monument. 3 Dragons + lvl 23 Warlock spellcaster will mow down ANYTHING. Anyway, I obviously had the Level needed for an Epic Quest.

Speaking of the Dragon Monuments, they need to be toned down: If you find the spot early and build it, you're unstoppable. 1 Dragon should be the maximum provided by the Shrine instead of the current three.

Hope this helps, and if needed I can provide the savegame.