Hello guys!
So here are the problems I encountered with my players entering Omu. It's not like I can't manage to handle them by myself but I think it's a really poor gamedesign (again) in their adventures. Let me share some of my previous/current issues with this adventure and maybe you will be able to avoid many of them.
My players are a 7th level party of wizard, rogue, barbarian, cleric and sorcerer. They already cleared most locations pointed on the map of Chult and they always do it ninja style. So far, we got two deaths in this campaign but I consider it fairly low when compared to their achievements in Chult.
They are kind of in some truce with Valindra, they established a new base for Camp Vengance in the jungle and with the money they got, they bought the supplies for them, weapons and armor. They hired more people to team up with Order of the Gauntlet. They made friends with Kir Sabal, Artus Cimber and they totally nailed Dungrunglung.
They are entering Omu now and are aware of Tomb of Nine Gods. Knowing my players, they will try to check the entrance to Tomb end they will do it without finding the puzzle cubes. "How" - you will ask? I am pretty sure they will polymorph whole team into tiny creatures (no matter how long it takes, or to write polymorph scrolls or they come up with something else) or come up with something else like polymorphing into Giant Ape which has 20+ strength and mining the entrance with giant hammer or pick.
But that's actually not so much of a problem, as it is with that they have tons of allies. Some of them are pretty powerful. They can literally come to Omu with tons of companions and flood the Tomb of the Nine Gods. And with so much firepower, they can easily bruteforce this dungeon and everything inside there.
Seriously, this whole Omu area is based on an assumption that player's chcaracters act like they are on a first level and have no resources and ideas to come up with.
They are heroes at this point of gameplay. They can use powerful magic and they are not suicidals. It's not like "hey, I am a powerful lvl 9 wizard who has its own magic guild but I will gladly go to this tomb and die". It's more like "I will crack this tomb and I won't play by the rules it wants me to play".
My players are very cunning and smart. They will come up with things I don't even imagine now and they surely won't risk their lives like idiots and just "go into the dungeon".
Tomb of Horrors was an adventure based on assumption "we are treasure hunters and there is a dungeon with treasures - let's go get it". Tomb of Annihilation is an adventure where you kind of save the world and you are not some random adventurer but at the point you reach this Dungeon, you can even call Elminster and tell him to bomb this place with magic nukes.
I'm kind of babyraging now cause I bought a ready to play product that is so problematic. Any thoughts comrades? I really don't even want to fix something that should be adressed by design team. At this moment I think I will let my players do what their imagination will tell them to do.