I like being inspired... :D

[White Tornado]

But I was also wondering: doesn't the 4E MOTP discuss the Isle of Dread as domain style plane instead of it's historical roots as a "normal" island south of The Known World? Not that it really ties in with the egyptian theme you want, but perhaps the 4E MOTP could provide some more inspiration.

In the 4E MotP (I love it), Domains of Dread are isolated pockets in the Shadowfell (p.51): surrounded by mist, you can accidently walk into a DoD, and then you're trapped inside. To leave you have to slay the master of the Domain, break his curse, unlock a secret, perform a ritual, or something else.

Even though its not RAW, you should be able to have a DoD floating around the multiverse, or floating in the Astral Sea as a small Astral Dominion (p.7, ch.5, etc). Maybe the DoD broke off from the Shadowfell and drifted into the Astral Sea. Mummies have a religious/divine flavour, don't they? Maybe the mummy moved his Domain to the Astral Sea himself, or the Raven Queen made the Shadowfell "spit" the mummy's DoD out into the Astral Sea.

Oh, and it's a pretty cool idea!

 

[Herobizkit]

*LOL* I've been reading 2nd edition Spelljammer books and recently finished up all ten seasons of Stargate. Consider this: with the aid of Spelljamming technology, allow the pyramid to be able to uproot and take flight. Perhaps the flying device will only work if the Gereater Mummy that was its owner is allowed to pilot the vessel...

 

[Aeolius]

I really dig the South American style pyramids. If you really wanted to, you could also change up the mummification; the corpses were mummified via salt.

And instead of Canopic jars, make Canopic homunculi - small constructs each containing either stomach, intestines, lungs, or liver. They remain "alive", so long as their host remains dead.