I don't think we need to defeat the Void Lords and Light Gods. This wouldn't need to be a direct rip off of Starcraft. This would be a Yaldabaoth sort of thing. The "Child of Chaos", in the Greek sense where "Chaos" means "Void", stealing the Light and becoming lord of the physical realm. The false God known as the Demiurge, of both light and darkness. Recognizing none as his master.
The goal would be to stop him before he truly mastered that power or was able to extend his grasp. And I think N'Zoth really would be the best fit, because the Demiurge is meant to be a creature born in the Void and he's been meddling with the Church of the Light for some time. He's infiltrated it so thoroughly that he could probably direct new doctrine and start spreading the belief that he is the one true god and speaker for the Light. When the Priests hear only the word of N'Zoth, and their sermons pass them onto the masses, how can he not be?
His current greatest servant is the Light beneath the Tides, and the Twilight Dragonflight hints at experimentation towards hybridization. Both Light and Darkness. Even the corrupted Dragon Soul still glowed in gold.