WMG: Dungeon Keeper Ami

The Avatar, like Ami, is originally from Earth.
In the original Dungeon Keeper, the Avatar is an Expy of the Player Character of Ultima. One of the more noteworthy traits of this particular Featureless Protagonist is that he hails from Earth; it's not beyond the realm of possibility that Amadeus shares this trait. The single largest piece of evidence suggesting this in-story, though, is that he sent Mercury a horseshoe magnet to explain that he'd figured out how she captured him; he wasn't seriously suggesting she had used such a magnet; rather, it's the shorthand visual cue for magnets that anyone exposed to Earth's mass media would immediately grasp.
  • Keep in mind that Amadeus has spent the last couple (subjective) decades (at least) in the Dungeon Keeper world; according to Ultima time tends to pass quicker in the Magical Land. It's been quite a while since he's had to deal with anything from outside the context of DK Land
    • We can explain the current apparent 1:1 synchronization being caused by Ami's connection to Mercury being constantly open and empowering her dungeon heart(s).
  • He may not be from the same Earth, but it keeps things tidier to assume that.

Adamantine is just like dwarf fortress.
It guards the way to hell.

This is based on a comment that Adamantineis used to denying the dark gods access to the world. At some point in the story, some one is going to dig too deep and unleash hidden fun stuff on the world. Which Ami will then defeat, with SCIENCE.
  • more evidence: the dwarfs are based on the ones from Dwarf fortress

Metallia is a powerful keeper who angered the dark gods
The two known things that can help such a keeper escape the darkness are life energy, and talking to a crystal dungeon heart they control. Life energy and a particular crystal are the two ways Metallia can be freed. In this case Metallia has found a way to protect herself from the dark gods, and influence the world beyond, in the mean time, likely by reverse-engineering some of the dark gods' powers.

Mukrezar imp butler will become a Casanova of Ami's female Imps.
because it's funny!
  • And because the Butler is obviously the result of when Mukrezar earns a perfected version of a monster and, being Mukrezar, picks an imp.

Pharaoh 90 from the Anime is actually the Unraveller of Mysteries in disguise
A powerful extraplanar being whose primary influence on mortals is to induce Mad Science and Sufficiently Analyzed Magic. Need we say more? The Light says they are trapping Ami in their world so the Dark Gods will not follow her back to Earth. What they don't realize is that the Unraveller of Mysteries has already been investigating other realities, using a specially fabricated personas to disguise itself from the Light Gods. The name isn't random, it's simply the Unraveller's naming convention: Persona Model Pharaoh, Instance 90. Dark Avatar Model Mistress, Incarnation 9. Which, incidentally, means that eventually Sailor Saturn will join the story and sacrifice herself to drop a Fantastic Nuke on the Unraveller.

The stronghold of the keeper who despoiled the dwarven lands was called Boatmurdered
Seriously, where else? It even has the corruption effects. It was not originally called Boatmurdered of course. It was named by the other dwarves for an incident when the keeper summoned a boat full of dwarven dignitaries, along with the boat, to outside the city. And informed them that, unfortunately, they would all be found to have died at sea. But not to worry: they would still get the traditional Viking Funeral. Cue the magma gates...