I'll post each encounter as I finish writing them, but first, the major tweaks to the overall campaign. Remember, my party started out at 5th level (and are well on their way to 10th now), so while these measures might seem draconic, it's really what's needed to keep the ToA random encounters relevant.
* perhaps the most significant change: you cannot long rest in the jungle!
That's right - you can camp for the night, but there's no benefit (other than what a short rest gives you, and the fact some items key to a new day, "dawn", "noon", "midnight" and the sort).
At rivers and coastline (beach hexes) you can attempt a DC 10 Con save to gain the benefits of a long rest during an 8 hour rest, but there are no rivers anywhere near Omu.
To be blunt - facing a couple of crocodiles or zombies simply isn't an interesting combat encounter at tier II, and if you could freely rest after having 0-2 of them, I would rather just skip them all "you meet and destroy three crocodiles and five zombies, now what?".
It's not worth even half an hour of game time to resolve one of the random encounters if the resource drain in lost hit points and spent spell slots doesn't mean anything. At levels 1-4 it would have been another story.
* the question then becomes "but can't they long rest at all?"
I currently think the Omu encounters (think of it as an overland dungeon) plus the Fane will be good for three days worth of adventuring. This means two long rests, assuming they arrive fully charged. Plus one more long rest, since sending them into the Tomb depleted would just be cruel.
This means at least three bouts of long rest. I have six adventurers, so that's 18 long rests. Plus, something might always go wrong, and in order to not force them to retreat back all they way to Lake Luo or Shilku Bay it's probably good design to feature at least one more bout they can find as precious treasure.
As for specifics, see the individual encounters.
* I didn't start the curse before now. I didn't want the players to feel forced into skipping the jungle content, and rushing straight to Omu. Now they're high enough level to use the curse as-is.
* the Yuan-Ti presence in Omu is beefed up considerably. The adventure paints a lost city with just a few dozen snake people, most of which are waiting for the party to descend into the Fane dungeon. For our purposes, this won't do - cynical players will simply say "we go straight to Ras Nsi, to wipe him out at the height of our power, so he can't ambush us when we're weaker".
As I read the adventure, it presupposes that the party wants to avoid the Yuan-Ti, and only enter the Fane when they realize they have to (because Ras Nsi has stolen a puzzle cube).
In my version, the south-eastern part of Omu is teeming with snake people, including "civilians" and young. Perhaps not a city's worth, but certainly a town's. At the very least over a hundred, enough to send a signal that a frontal assault is probably too dangerous even for mighty heroes. This is also necessary to explain the seemingly limitless hordes that can harass the party, without having to reduce the Yuan-Ti presence in/under the Royal Palace.
Related to that, I'm having three factions of Yuan Ti. The party can (must?) ally themselves either to one of them, or to the Red Wizards. It is Fenthaza, not Ras Nsi, who steals the puzzle cube. Why would Ras Nsi want to risk everything by drawing the ire of adventurers? It makes much more sense that Fenthaza makes the heroes believe Ras Nsi has the cube - after all, she wants him dead!
* there's a way to actually find out the cool backstory of the adventure!
The Tabaxi hunters provide much info. I'm placing a Minotaur Potion seller to reveal the ancient history. And I want the city encounters to explicitly tell the DM to hand out hints about Acecerak - not just the only (unlikely) book event they walk around the city to approach from above the waterfall.
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(reserved - I might realize some other general pointer as I go)
* finally, as you can see from the map, I'm intending to reveal this map to the party. This way they hopefully feel they have a whole city to explore, while still getting some sense of progression, since they will gain the meta knowledge of what spots are "important". As you can see, I've added several map keys - precisely to allow some to be more important than others.
