How much time do you have?

For a general overview, there's three universes in my lore. These are:

• Mithraia, my first and main world. Future!Mithraia is technically a separate timeline from the original Mithraia, but it's virtually identical until you get to the point where the original timeline ends. Future!Mithraia contains the Nephilim universe too, as well as some characters of mine from neither. Mithraia the universe is not to be confused with Mithraia the planet, the center of Mithraia the universe.
• Nephilim is, admittedly, the A2 universe from Homestuck but in the future (specifically 1,775 years after when SGRUB happened in the original comic) and where I care more about the non-Alternians. Also, the Alternian military is a bit more ethical/practical.
• Gaia/Gates of Purgatory is completely separate from the other two universes and it's also very empty, the only celestial bodies in this universe are the planet of Gaia and its star. Heaven, Hell, and Purgatory exist here but Heaven and Hell suck while Purgatory is effectively a doomsday device. Also pretty much every species hates/at least distrusts each other except for Humans and Elves.