Four Major Campaign Villains for Athanor

While it's possible to just do a game of exploration using the Athanor hex map, or to do a long-term dungeon crawl in the Undercity below Zamora, my play style is more to create a campaign where players can actually face a big villain and develop their own sense of a larger purpose. And, frankly, I haven't had a group yet where that wasn't something that they responded well to, even when I was running AD&D 1e back in the early 1980s.
So, in order to provide some room for that kind of gaming, here are four ideas for the Big Bads behind major plots on Athanor. Personally, I would use at least two of these ideas, if not all four.

1. The Witch Kings of Ylum: A handful have survived, locked in deep tombs, as liches. If awakened, they will work on awakening still other witch-kings and strange sorcerous armies of undead and worse.
2. The Machines of Aquila: a handful of intelligent and semi-intelligent doomsday devices created by the Empire of Aquila as part of its war on Ylum survive. Seeing the use of magic in the world at large, these machines think Ylum has managed to win the war and, if awakened, these machines will begin to purge the world.
3. Mysterious Alien Civilization: Survivors of a crash in the Starfall mountain, the vaguely reptilian, grey-skinned aliens are masters of strange technology. They are amoral, ruthless, and dedicated to conducting experiments on all life in order to find a wy to extend their own.
4. The Lords of the Moons: Selune is home to a civilization of alien creatures that live under the surface of the moon. Looking like large jellyfish with brains floating in their centers, the Selunians have powerful psychic powers, advanced technology, and spacecraft. They are served by a race of pale, primitive bird-people with iron-sharp claws called the Corbin. The other moon, Miera, is home to several mechanized, idyllic dome cities in good repair, populated by gold-skinned, pampered urbanites with no ability to survive outside their cities, and no knowledge of the past. The Selunians use them as food, and have built a religion around sacrifices of Mierans to Selunians. There is a problem with the Selunians' food supply, and now the Selunians are beginning to raid Athanor.