And apparently, we have a new entry.
Tim O'Neil of the Hurting sent me an e-mail about Rise of Apocalypse, a 1996 X-Men mini series :
I don't know if you're aware but there was actually a fourth component to the Rama Tut meta-crossover, published in the mid 90s. During the "Rise of Apocalypse" mini series it is established that the immortal X-Men villain Apocalypse was a slave of the Pharaohs during the reign of Rama Tut - and that (if memory serves me well) there was a slave revolt led by Apocalypse at the exact same time the FF were fighting Rama Tut.
Don't know if you ever saw that book - it's one of the better series Marvel spat out in the 90s. Not exactly a banner era for the company.
Yeah, this one was definitely off my radar, as I ignored the ocean of X-Men books back then. I never had any interest in Apocalypse, and I had no idea that Rise of Apocalypse had anything to do with the cross-time crossover, but apparently, Apocalypse was a slave owned by Rama-Tut, and rose to power after the events of Fantastic Four #19. There's a pretty thorough synopsis here, not far down the page.
I checked for Rise of Apocalypse at my local comic shop, but no luck. Thus a comic series that I couldn't have been less interested in last week becomes my holy grail. It seems I have some searching ahead of me, but if I can find this story, you'll be invited to "Meet Me at the Sphinx" for one last chapter.