Hi!
I am running this campaign as a GM, with 2 players, using the dual class option and making them 1 level higher than the normal milestones and we are having a blast, we are in the middle of book 2.
But I feel my players will not like the idea of fully ignoring the egg, while they go around doing unrelated archeology and diplomacy. I think books 2 to 5 are great episodes, but they are episodes, with self contained stories and little connective tissue.
Here is my idea. Suggestions are welcome.
Salithiss thinks the egg is a serpent one because a halfling named Thiarvo tried to sell it to him, claiming that. He finally sold it to Koride, who paid more. That's how the Serpent Folks know the egg is in Magaambya. Thiarvo got that egg in Bloodsalt, and he doesn't really know what it is.
Once the players get to Bloodsalt, they discover Kiutu was destroyed by some insects, including giant beetles and swarms of locusts (I want the insect theme running for at least a bit longer). It needs more repairs. They go to clear Bloodsalt, meet with Thiarvo, who is obviously a lier, cheater, and scoundrel, but not a murderer. They talk about Bloodsalt, and if/when the players defeat him in a social encounter, he finally leaves, telling them he is trying to find the mythical Golden City, which is a much better target anyways. He hints that he might know a place in Mzali with a clue, boasting about that.
The players enter in Bloodsalt, they discover Ixame and the Petrified Eggs. Ixame half-dead status is caused by something else: he is half devoured by a Hellwasp Swarm (when he exhales his final breath, instead of doing breath weapon damage, he frees the wasps). The AP says that King of biting Ants created the Vesicant Egg through his will, that he hid in a small ant, and then he gathered more ants. It doesn't say how exactly the egg was created. Here is my take: the Flying people of Bloodsalt weren't dragon men. The billowing wings they developed were butterfly wings, they believed in Desna (which gives a connection to one of my players, a cleric of Shimye-Magalla, and Ixume was their protectors. The will of King of Biting Ants came to Bloodsalt, infected one of the eggs, and attracted insects. The insects weren't normal, and a Swarm of Wasps took him while he was sleep (mechanically, Hellwasps). Then the Dead Man's Breath came and everyone who couldn't flee, died.
The Knights of Abendego are members of a defected Chelaxian warship going rogue after Vidrin got their defense, The Lord of Flies. This can lead to interesting tension with Ignaci Cantarells, who is Chelaxian, but innocent, and how the players deal with the negative reception Ignaci has in Jula. The Knights are followers of Baalzebub, and they summon, control and worship some Lovaloch devils, so they wear tridents because of that. Lovaloch and Hellwasps (and Accursed Devils,) also fit the theme of insects, and even if they aren't exactly under control of the Vesicant Eye, they "feel" it. They aren't there because if it, though, they are looking to sacrifice people to get information about something different: the location of Osibu, the Golden City, something that ambitious people like the followers of The Lord of Flies should be naturally attracted to, just because it is made of gold, or that says the myth.
The players defeat Abjal and the crew that landed on Jula, but the Lord of Flies leave the coast to not be seen again, for now.
After that, the PC have a clue leading to Mzali, but not a connection between Mzali (or Osibu). But that's ok. Here is where Koride, Janatimo and Oyembe decide that Koride will hide the egg within the Iobane temple. They might already know a bit about the egg, and the connection to Jatembe and King of Biting Ants, so it makes sense that the Iobane, a cult dedicated to keep the Red Door closed, can help to keep it safe, as the egg can't be destroyed anyways.
So the Magaambya rulers send a delegation, with the idea of securing a seal to be able to study the Temple, not an easy task. There are other delegations there, including one from the Áspid Consortium, who want to secure a better deal than the Anthusis Traveler Merchant Guild. In order to do so, they are giving one of the ambitious Council rulers money, information, and power: Worknesh. Themba Sufu suspects this, but he can't prove it. It is Worknesh who sent the Reborns. Thiarvo is also there. He helps the players when he can, but he is also a nuisance, breaking rules, and being always very close to make Walkena cross the line and kill everyone. Thiarvo help is invaluable, though: he has half of the Golden plate that works as a map to Osibu. He will memorize it when the players put both halves together, and then he sells the info to the best bettor: the Aspid Consortium.
Who will present themselves in Osibu, with a brigade of Knights of Abendego, a bunch of Steam Tanks (replacing the Sun Spires), Worknesh, and some Sun Warriors loyal to him. Worknesh, with the help of the Consortium, entered the Temple of Eclipse after the PC leave it, and touching a sun mote there, becomes an Avatar of the Sun, with the stats of the Avatar of Walkena.
Once the PC beat him, they learn about Jatembe, Akiton, etc.
Book 5 plays as is, with one minor change: Koride entered the Cathedral of Nothingness with the Egg, believing that only there it could be contained, and the Iobane are furious about that, as they have a vow to never enter that place.
The rest of book 5 and 6 goes unchanged.