I just finished DMing Descent into Avernus book for my group of 6 players as part of our campaign. We started the book from Chapter 2 when they were all level 5, and they reached level 11 when we finished it last week (we use milestone leveling, and I have full control of it). It took us about 9 months (we play weekly). I think it was very successful, as some players told me they really enjoyed it. I figure I can write up something to share my experience of running it because I did twist and change some of it.
I know a lot of people say Chapter 1 is very difficult for low level PCs. I didn't use it so I wouldn't know. I like the detailed description of Baldur's Gate the book has to offer though.
------------ Spoiler-free ------------
What I like about it?
This is probably my favorite 5e module, not because it is the best written, but because it has the greatest potential to be very very awesome. I say this for a number of reasons. But each reason could be the reason a DM would either love it or hate it. It really depends on what type of DM you are and what type of player party you are with.
Dynamic environment. No matter which part of the book, no matter where your party is in Avernus, there is just a lot going on in the environment. There is almost no place in Avernus that's just a static dungeon with certain number of monsters waiting for the party to kill with video-game mentality. Almost every encounter is dynamic, and that makes it a very engaging experience. Role playing players and tactic players don't ever get bored.
Awesome villains (plural). Most monsters in Avernus have their own reasoning to do whatever they are doing. It provides a lot of role-playing opportunities to avoid combat, which really adds a lot of tension to the combats once they occur. Those temporarily friendly monsters do add up fast and the PCs have to keep them that way when battling other monsters, which makes every encounter (both combat and social) very interesting. It requires DM to track a lot of extra things though, but it's all worth it.
Very clear goal. It doesn't really require the PCs to care much about anything to have a party with a shared goal and bound with each other once they get to Avernus. Everyone naturally just want to escape from Avernus and therefore highly motivated.
What I don't like about it?
Quite a few potentially-very-exciting encounters are short in pages. I had to add a lot of homebrew to enrich them. I will go through them in the spoiler section.
What the players like about it?
My players are all experienced players. Our last two campaigns (same group, me as a player) were also in Forgotten Realms (Tiamat modules and Elemental Evils module as the first one, then Tomb of Annihilation as the second short one). In our second campaign the players did feel they were a little tired of Forgotten Realms and wanted to have something new. This module, however, gave them a lot of whole new experiences.
What the players don't like about it?
Some players don't like railroading adventures, and this is certainly one of the most railroading ones in 5e. It's completely subjective but we all like making our own decisions. However, they also told me that the later part of this adventure is getting way better and they really liked it even if it was still very railroading.
I think the reason behind that is that this railroading is done right: it's not "no matter what decisions players make, it ends up the same"; it is instead "the players just don't have much of a choice". There is usually one clear path of what the party needs to achieve as next step, in order to escape Avernus without selling their souls or facing even worse consequences (and also a LOT of choices that are obvious, and obviously bad). It also adds a lot of tensions and excitement to the encounters.
------------ Spoiler Below! ------------
Now, I will go through each chapter to share what I like about it, what I don't like about it, and what changes I made to it.
Chapter 1
We didn't run Chapter 1, so we skipped the thread of Shield of the Hidden Lord. I changed its origin so that it becomes a loose end at the end: Zariel made two artifacts, the Companion to trap an angel, and the Shield to trap a devil. The Companion was used to drag the holy city of Eltural down to Avernus, while the Shield will be used to drag down the sinister city of Baldur's Gate. Now there will be a potential future adventure to track down and deal with the Shield.
Chapter 2
This is the real start of the Avernus adventure. You can completely skip Chapter 1, swap it with another starter adventure, what have you. The bottom line is, the PCs need to get to the fallen city of Eltural.
In my campaign, the PCs were teleported there in a wild magic zone. The benefit and the challenge to do that is that the PCs may be clueless of what's going on when they appear to be in the city. They may need to find survivors and interact with them to learn where they are and what's happening. This part of the narratives also may not be a players' choice, which, if only happens once in a while, may not be a big deal.
This chapter is also the opportunity to implant the adventure-in-hell feelings into the players' mind. Let them know they are in big trouble.
Devils (and their cultists) here are going to kill the PCs because they want PCs' souls, so they don't stop at dropping PCs to unconsciousness. They will follow up with killing blows.
Unknown entities proposing contracts when a PC is about to die (really die, not drop to 0 HP).
No where to find food and drink, and they all taste awful.
No "base of operation".
Etc.
I didn't change this chapter much. The PCs met Lulu in the catacombs under the High Hall.
Chapter 3 (First Half)
I didn't change the first half much (before they choose the path of devils or demons).
Get to Fort Knucklebone in a Mad Max style chase. (My party managed to rob a Demon Grinder from a warlord.)
In Fort Knucklebone, Mad Maggie does the ritual to restore part of Lulu's memory of Haruman.
They find one of Zariel's lieutenant Haruman, but that turns badly.
Lulu is captured by the hellwasps.
PCs rescue Lulu from hellwasp hive.
The Thing I don't like
The development at this point in the book is the one thing I dislike very much. Lulu provides two leads: where demons manifest and where demons are destroyed. If you (as DM) think about it with the whole adventure as context, you will find neither option makes any sense. There is no where you can find in the whole module why either place is important, or why Lulu would think them important. If your party investigates Lulu's claim further, you as DM basically don't know what to say at all.
Also, there is no role playing reason to choose between the two paths. They are blind choices. Players will have no idea what the consequence is for either choice. What do you want them to base on to make this choice?
So I ended up just not giving my party that development paragraph. The party did have a few options to go: they basically need to find some powerful figures in Avernus in order to gain information. They had two options based on what they knew: Bel and Mordenkainen. And basically saving Lulu provided no immediate value at all.
Things I like
Infernal machine chase is very exciting.
Fort Knucklebone's social encounters are very fun, if DM plays all the NPCs and especially the redcaps and madcaps correctly.
Haruman's Hill is well designed. The atmosphere there really brings out the feeling of being in Hells. The interaction between stirges and vampire is brilliant.
Hellwasp hive is well designed. My players marveled when they learned that the angel souls are what keep the hive afloat.
Chapter 3 (Second Half)
The second half of this chapter is the part I changed the most. The book basically describes 16 places PCs can visit, and use two quest chains to put them together. After the awkward development at the end of hellwasp hive encounter, everything else ran pretty smooth in my campaign, although I needed to change quite a few things around.
My suggestions for running this part
Know your party. You as DM need to know what types of encounters work for your players and what don't. Know meeting which NPCs is most exciting for them.
Pick out places and encounters that would work for your party, and find a way to put them together as your quest chain.
Things I ran
I picked these NPCs because I knew encountering them would be very exciting to my group: Mordenkainen the legendary wizard, Arkhan the champion of Tiamat, Bel the pit fiend, and Olanthius the death knight. Therefore I planned my own quest chain, and tried to cover most of them.
Tower of Urn
First I let the party choose between Mordenkainen and Bel, and either way led to Arkhan (who may know Olanthius). They will also need to go to the wrecked flying fortress to obtain the orb of dragonkind as a leverage to negotiate with Arkhan. (I changed the location of the orb of dragonkind.)
It took me some effort to come up with the reason why either Mordenkainen or Bel would give up a powerful artifact like the orb of dragonkind, but basically the idea is to send the PCs to a big quest in exchange for both the information that "Arkhan is the next lead" and "where to find what Arkhan wants".
My party chose Mordenkainen (a wise choice). I homebrewed his tower and let the PCs meet him close up in the tower. He sent the PCs to the White Plume Mountain (I really wanted to gear up my party) and capture an efreeti in a magic bottle. He use astral projection to send PCs to the no-way-out (DM collapsed all the entrances/exits) dungeon, and they finished the quest.
Wrecked Flying Fortress
Then PCs went to the wrecked flying fortress to get the orb of dragonkind. This quest was an unexciting one.
Arkhan's Tower
One of my PCs was a paladin, and he suggested to propose a duel to Arkhan. If Arkhan wins, he can have the orb; if he loses, he needs to tell the PCs where to find Olanthius. I thought that idea was brilliant. The only problem is that it will be a one-man show while other players would just be watching. So I changed it to a group duel. The party vs. Arkhan's party (with Krull, Torogar, Chango the manticore, and Asojano the chimera). You can tell the CR is through the roof, but with the weapons from White Plume Mountain and right tactic (the party wizard wall-of-force Arkhan and the manticore in the 1st round and maintained his concentration for the entire combat thanks to the war caster feat), they managed to pull it off (with one casualty). Most players loved it. They said it was a crazy fight.
Crypt of the Hellriders
My party went there, treated the Hellriders' ghosts with respects, and finally gained the alliance from Olanthius.
Arches of Ulloch
Olanthius showed PCs the arches and after this, the PCs used the arches to travel (Kostchtchie’s Maw, Bleeding Citadel, then back to Eltural).
Kostchtchie’s Maw
PCs freed the demon lord to create a distraction so that Olanthius could be willing to lead the PCs to the Bleeding Citadel.
Things I don't like
The content about Mordenkainen. This is one of the most famous NPCs! The players would be thrilled if they get to meet him and know him and interact with him. Yet the book only has one page, ONE PAGE, for him! The encounter in the book may become the most disappointing encounter in the whole adventure. The PCs may try to find a way to get more of his attention, but there is nothing in the book you can use to expand that encounter.
Another thing I don't like is that Olanthius (Crypt of the Hellriders) is only in one of the quest chains, but that may decrease the ability check DC for pursuading Zariel at the end by 5. That means the party will have a more difficult time at the end as a consequence of blindly choose the path where "demons are destroyed". That just does not make any sense.
The crypt of the Hellriders is also not a very good dungeon. Many rooms are repetitive. A suggestion for DM who would run it: give ghosts names (PHB Human race, Chondathan Names), and simple background (occupation before becoming a Hellrider, etc.). That would slightly ease the boredom.
Similarly, I don't like is the simplicity of Kostchtchie’s Maw in the book. This is a prison for a demon lord n Hells. It needs to feel like one. Things I added to this place:
Magic darkness at the bottom. I think this should be given. Devils uniquely have devil's sight. They surely want to use it as much as they can.
Tar pit at the bottom where PCs will sink (and that's in the magical darkness).
Oh, by the way, the tar pit is flammable, so when the hell hounds come down, the first thing they do is to use their fire breath to ignite the whole tar pit (a wall of fire pushing through the whole area).
These additions really brought this place to life.
The last thing I don't like is that there are quite a few places and encounters in the quest chains in the book are just not exciting at all. Mirror of Mephistar, pit of Shummrath, demon zapper, and Bel’s forge could be interesting. I couldn't fit them into my quest chain, but I feel like my quest chain is already a little too long. The book also left out a lot of interesting places, Tiamat's dragonspawn pit for example.
Things I like
The NPCs. To be specific, the four NPCs I mentioned before: Mordenkainen the legendary wizard, Arkhan the champion of Tiamat, Bel the pit fiend, and Olanthius the death knight. These NPCs are very powerful, yet the PCs don't always have to fight them, because theses characters are very enriched. Each of them has his own goals and reasons and meanings. With some work, they can make very memorable encounters.
Chapter 4
The best written chapter in the book IMO. I ran it almost exactly as written and it was truly great.
Things I like
The scab is a very challenging dungeon because it should not give the party any chance to even short rest, and the demons and gnolls should move around. The monsters a scouting PC discovered may not stay there when the PCs go to that spot. Use the shadow demon smartly. Make sure it scouts and PCs and goes back to report, then an ambush will be set up for the PCs.
Idyllglen is a very engaging encounter chain. Make sure you showcase Yeenoghu's power. Use his legendary actions to charge to the PCs. Yeenoghu is really going to shine once PCs are in melee combat with it.
The thing I don't like
Zariel's sword's transformation when becoming attuned. That's some BS design to have identity change and permanent true sight. My campaign will continue after this module, and my players want to keep playing their character. One of them would not be able to do that if his character forget everything and becomes a half-angel. I also would never grant my players permanent true sight. That will disable so many plots in the future adventures. I removed the identity change and the true sight in my run. The paladin (an oathbreaker) in my party claimed the sword by redeeming himself from being an oathbreaker and swearing a new oath to Lathander.
Chapter 5
My party has been trying to do the right things, so naturally we went to Zariel's redemption route. That's supposed to be the happy ending of this module, and that ending is probably the biggest problem in this book.
See in the book, once Zariel is redeemed, she will release the planetar and the planetar will return the city back to the material plane. That's it. That doesn't make any sense! If Zariel becomes an angel again, she basically violated her contract with Asmodeus, and I cannot believe Asmodeus would just let it go like that. There has to be consequences.
So in my run of it, I added a little drama:
After Zariel breaks the chains and release the planetar, the planetar will go do his thing, then Asmodeus shows up and ask Zariel, "You are not thinking about breaking your contract, are you?"
Lathander then shows up and ask back, "You are not thinking about breaking YOURS, are you, Asmodeus?" And he is referring to that the people in Eltural didn't die in material plane, so even if some are evil or corrupted, Asmodeus still don't have the ownership of their souls, according to Pact Primeval.
Through the conversation between the gods, it is explained that the chains were preventing the gods like Lathander from entering Eltural (and now the chains are broken).
Zariel steps out and say to the gods that her contract is to serve Asmodeus to rule Avernus and fight the blood war in exchange of sparing her life, which can be voided if she dies. Then she kills herself to be free of Asmodeus.
Then after that, I decided to add more drama from some other factions. Basically if Eltural is going to material plane, that will be a perfect opportunity for anyone in Avernus to get a free ride, especially for Tiamat's dragons. On the other hand, devils don't want Eltural to go back. So seeing the city starts ascending, the devils will try to swarm the planetar, and the chromatic dragons will try to intercept. The evil dragons will prevail and they all land in the city for the ride, and the PCs just don't have enough power to stop them. But when the city is through, a legion of metallic dragons are waiting (because Bahamut is a close ally of Torm).
After the last session, one of my players told me that it was the best ever ending he had played in D&D. I think it really worked out very well as a cinematic climax. The book sadly doesn't have anything like that. IMO it really misses the mark there.
Summary
There are four major plot issues that need to be fixed in the book:
The development at the end of hellwasp nest encounter. (Two random places are provided by Lulu for no good reason.)
Olanthius should be in the main plot line, not a branch plot line. (It's unfair to the group who chooses the branch plot line without him.)
Transformation by Zariel's sword. (Personality change is ruining a player character with no respect; and true sight is going to ruin the campaign.)
The ending of Zariel's redemption. (Zariel breaks her contract without any consequence.)
Things to do to make this module much better:
Customize the quest chain (Chapter 3b) to be best fit to your party.
There are many places/encounters that could have be written better: Mordenkainen, The crypt of the Hellriders, Kostchtchie’s Maw, and many others in the quest chains (Chapter 3b).
If you can do all above as a DM, this adventure is going to be even better than Curse of Strad.
Thanks for taking the time to do the writeup with notes.
Were there a lot of RP opportunities (and bargains) for the characters to engage in once the plot was going? Does it end up being a lot of faction and ally management?
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"An' things ha' come to a pretty pass, ye ken, if people are going to leave stuff like that aroound where innocent people could accidentally smash the door doon and lever the bars aside and take the big chain off'f the cupboard and pick the lock and drink it!"
Thanks for taking the time to do the writeup with notes.
Were there a lot of RP opportunities (and bargains) for the characters to engage in once the plot was going? Does it end up being a lot of faction and ally management?
There are a lot of RP opportunities but the plot is still pretty linear. I don't think RP can make any step change to the plot.
There are quite a few factions but there isn't much politics.
It is a very fast-paced adventure, so not much ally management can be done. Most alliances are just one-time deal. You can't really have any long-term trust to anyone in that place.
However, I could be biased because my party doesn't have any bard or rogue. They are an eldritch knight, a gunslinger, a barbarian, a paladin, a bladesinger, and a GOO warlock (yeah, basically 5 warriors and 1 spellcaster, pretty hardcore).
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I just finished DMing Descent into Avernus book for my group of 6 players as part of our campaign. We started the book from Chapter 2 when they were all level 5, and they reached level 11 when we finished it last week (we use milestone leveling, and I have full control of it). It took us about 9 months (we play weekly). I think it was very successful, as some players told me they really enjoyed it. I figure I can write up something to share my experience of running it because I did twist and change some of it.
I know a lot of people say Chapter 1 is very difficult for low level PCs. I didn't use it so I wouldn't know. I like the detailed description of Baldur's Gate the book has to offer though.
------------ Spoiler-free ------------
What I like about it?
This is probably my favorite 5e module, not because it is the best written, but because it has the greatest potential to be very very awesome. I say this for a number of reasons. But each reason could be the reason a DM would either love it or hate it. It really depends on what type of DM you are and what type of player party you are with.
Dynamic environment. No matter which part of the book, no matter where your party is in Avernus, there is just a lot going on in the environment. There is almost no place in Avernus that's just a static dungeon with certain number of monsters waiting for the party to kill with video-game mentality. Almost every encounter is dynamic, and that makes it a very engaging experience. Role playing players and tactic players don't ever get bored.
Awesome villains (plural). Most monsters in Avernus have their own reasoning to do whatever they are doing. It provides a lot of role-playing opportunities to avoid combat, which really adds a lot of tension to the combats once they occur. Those temporarily friendly monsters do add up fast and the PCs have to keep them that way when battling other monsters, which makes every encounter (both combat and social) very interesting. It requires DM to track a lot of extra things though, but it's all worth it.
Very clear goal. It doesn't really require the PCs to care much about anything to have a party with a shared goal and bound with each other once they get to Avernus. Everyone naturally just want to escape from Avernus and therefore highly motivated.
What I don't like about it?
Quite a few potentially-very-exciting encounters are short in pages. I had to add a lot of homebrew to enrich them. I will go through them in the spoiler section.
What the players like about it?
My players are all experienced players. Our last two campaigns (same group, me as a player) were also in Forgotten Realms (Tiamat modules and Elemental Evils module as the first one, then Tomb of Annihilation as the second short one). In our second campaign the players did feel they were a little tired of Forgotten Realms and wanted to have something new. This module, however, gave them a lot of whole new experiences.
What the players don't like about it?
Some players don't like railroading adventures, and this is certainly one of the most railroading ones in 5e. It's completely subjective but we all like making our own decisions. However, they also told me that the later part of this adventure is getting way better and they really liked it even if it was still very railroading.
I think the reason behind that is that this railroading is done right: it's not "no matter what decisions players make, it ends up the same"; it is instead "the players just don't have much of a choice". There is usually one clear path of what the party needs to achieve as next step, in order to escape Avernus without selling their souls or facing even worse consequences (and also a LOT of choices that are obvious, and obviously bad). It also adds a lot of tensions and excitement to the encounters.
------------ Spoiler Below! ------------
Now, I will go through each chapter to share what I like about it, what I don't like about it, and what changes I made to it.
Chapter 1
We didn't run Chapter 1, so we skipped the thread of Shield of the Hidden Lord. I changed its origin so that it becomes a loose end at the end: Zariel made two artifacts, the Companion to trap an angel, and the Shield to trap a devil. The Companion was used to drag the holy city of Eltural down to Avernus, while the Shield will be used to drag down the sinister city of Baldur's Gate. Now there will be a potential future adventure to track down and deal with the Shield.
Chapter 2
This is the real start of the Avernus adventure. You can completely skip Chapter 1, swap it with another starter adventure, what have you. The bottom line is, the PCs need to get to the fallen city of Eltural.
In my campaign, the PCs were teleported there in a wild magic zone. The benefit and the challenge to do that is that the PCs may be clueless of what's going on when they appear to be in the city. They may need to find survivors and interact with them to learn where they are and what's happening. This part of the narratives also may not be a players' choice, which, if only happens once in a while, may not be a big deal.
This chapter is also the opportunity to implant the adventure-in-hell feelings into the players' mind. Let them know they are in big trouble.
I didn't change this chapter much. The PCs met Lulu in the catacombs under the High Hall.
Chapter 3 (First Half)
I didn't change the first half much (before they choose the path of devils or demons).
The Thing I don't like
The development at this point in the book is the one thing I dislike very much. Lulu provides two leads: where demons manifest and where demons are destroyed. If you (as DM) think about it with the whole adventure as context, you will find neither option makes any sense. There is no where you can find in the whole module why either place is important, or why Lulu would think them important. If your party investigates Lulu's claim further, you as DM basically don't know what to say at all.
Also, there is no role playing reason to choose between the two paths. They are blind choices. Players will have no idea what the consequence is for either choice. What do you want them to base on to make this choice?
So I ended up just not giving my party that development paragraph. The party did have a few options to go: they basically need to find some powerful figures in Avernus in order to gain information. They had two options based on what they knew: Bel and Mordenkainen. And basically saving Lulu provided no immediate value at all.
Things I like
Chapter 3 (Second Half)
The second half of this chapter is the part I changed the most. The book basically describes 16 places PCs can visit, and use two quest chains to put them together. After the awkward development at the end of hellwasp hive encounter, everything else ran pretty smooth in my campaign, although I needed to change quite a few things around.
My suggestions for running this part
Things I ran
I picked these NPCs because I knew encountering them would be very exciting to my group: Mordenkainen the legendary wizard, Arkhan the champion of Tiamat, Bel the pit fiend, and Olanthius the death knight. Therefore I planned my own quest chain, and tried to cover most of them.
Tower of Urn
First I let the party choose between Mordenkainen and Bel, and either way led to Arkhan (who may know Olanthius). They will also need to go to the wrecked flying fortress to obtain the orb of dragonkind as a leverage to negotiate with Arkhan. (I changed the location of the orb of dragonkind.)
It took me some effort to come up with the reason why either Mordenkainen or Bel would give up a powerful artifact like the orb of dragonkind, but basically the idea is to send the PCs to a big quest in exchange for both the information that "Arkhan is the next lead" and "where to find what Arkhan wants".
My party chose Mordenkainen (a wise choice). I homebrewed his tower and let the PCs meet him close up in the tower. He sent the PCs to the White Plume Mountain (I really wanted to gear up my party) and capture an efreeti in a magic bottle. He use astral projection to send PCs to the no-way-out (DM collapsed all the entrances/exits) dungeon, and they finished the quest.
Wrecked Flying Fortress
Then PCs went to the wrecked flying fortress to get the orb of dragonkind. This quest was an unexciting one.
Arkhan's Tower
One of my PCs was a paladin, and he suggested to propose a duel to Arkhan. If Arkhan wins, he can have the orb; if he loses, he needs to tell the PCs where to find Olanthius. I thought that idea was brilliant. The only problem is that it will be a one-man show while other players would just be watching. So I changed it to a group duel. The party vs. Arkhan's party (with Krull, Torogar, Chango the manticore, and Asojano the chimera). You can tell the CR is through the roof, but with the weapons from White Plume Mountain and right tactic (the party wizard wall-of-force Arkhan and the manticore in the 1st round and maintained his concentration for the entire combat thanks to the war caster feat), they managed to pull it off (with one casualty). Most players loved it. They said it was a crazy fight.
Crypt of the Hellriders
My party went there, treated the Hellriders' ghosts with respects, and finally gained the alliance from Olanthius.
Arches of Ulloch
Olanthius showed PCs the arches and after this, the PCs used the arches to travel (Kostchtchie’s Maw, Bleeding Citadel, then back to Eltural).
Kostchtchie’s Maw
PCs freed the demon lord to create a distraction so that Olanthius could be willing to lead the PCs to the Bleeding Citadel.
Things I don't like
The content about Mordenkainen. This is one of the most famous NPCs! The players would be thrilled if they get to meet him and know him and interact with him. Yet the book only has one page, ONE PAGE, for him! The encounter in the book may become the most disappointing encounter in the whole adventure. The PCs may try to find a way to get more of his attention, but there is nothing in the book you can use to expand that encounter.
Another thing I don't like is that Olanthius (Crypt of the Hellriders) is only in one of the quest chains, but that may decrease the ability check DC for pursuading Zariel at the end by 5. That means the party will have a more difficult time at the end as a consequence of blindly choose the path where "demons are destroyed". That just does not make any sense.
The crypt of the Hellriders is also not a very good dungeon. Many rooms are repetitive. A suggestion for DM who would run it: give ghosts names (PHB Human race, Chondathan Names), and simple background (occupation before becoming a Hellrider, etc.). That would slightly ease the boredom.
Similarly, I don't like is the simplicity of Kostchtchie’s Maw in the book. This is a prison for a demon lord n Hells. It needs to feel like one. Things I added to this place:
These additions really brought this place to life.
The last thing I don't like is that there are quite a few places and encounters in the quest chains in the book are just not exciting at all. Mirror of Mephistar, pit of Shummrath, demon zapper, and Bel’s forge could be interesting. I couldn't fit them into my quest chain, but I feel like my quest chain is already a little too long. The book also left out a lot of interesting places, Tiamat's dragonspawn pit for example.
Things I like
The NPCs. To be specific, the four NPCs I mentioned before: Mordenkainen the legendary wizard, Arkhan the champion of Tiamat, Bel the pit fiend, and Olanthius the death knight. These NPCs are very powerful, yet the PCs don't always have to fight them, because theses characters are very enriched. Each of them has his own goals and reasons and meanings. With some work, they can make very memorable encounters.
Chapter 4
The best written chapter in the book IMO. I ran it almost exactly as written and it was truly great.
Things I like
The scab is a very challenging dungeon because it should not give the party any chance to even short rest, and the demons and gnolls should move around. The monsters a scouting PC discovered may not stay there when the PCs go to that spot. Use the shadow demon smartly. Make sure it scouts and PCs and goes back to report, then an ambush will be set up for the PCs.
Idyllglen is a very engaging encounter chain. Make sure you showcase Yeenoghu's power. Use his legendary actions to charge to the PCs. Yeenoghu is really going to shine once PCs are in melee combat with it.
The thing I don't like
Zariel's sword's transformation when becoming attuned. That's some BS design to have identity change and permanent true sight. My campaign will continue after this module, and my players want to keep playing their character. One of them would not be able to do that if his character forget everything and becomes a half-angel. I also would never grant my players permanent true sight. That will disable so many plots in the future adventures. I removed the identity change and the true sight in my run. The paladin (an oathbreaker) in my party claimed the sword by redeeming himself from being an oathbreaker and swearing a new oath to Lathander.
Chapter 5
My party has been trying to do the right things, so naturally we went to Zariel's redemption route. That's supposed to be the happy ending of this module, and that ending is probably the biggest problem in this book.
See in the book, once Zariel is redeemed, she will release the planetar and the planetar will return the city back to the material plane. That's it. That doesn't make any sense! If Zariel becomes an angel again, she basically violated her contract with Asmodeus, and I cannot believe Asmodeus would just let it go like that. There has to be consequences.
So in my run of it, I added a little drama:
Then after that, I decided to add more drama from some other factions. Basically if Eltural is going to material plane, that will be a perfect opportunity for anyone in Avernus to get a free ride, especially for Tiamat's dragons. On the other hand, devils don't want Eltural to go back. So seeing the city starts ascending, the devils will try to swarm the planetar, and the chromatic dragons will try to intercept. The evil dragons will prevail and they all land in the city for the ride, and the PCs just don't have enough power to stop them. But when the city is through, a legion of metallic dragons are waiting (because Bahamut is a close ally of Torm).
After the last session, one of my players told me that it was the best ever ending he had played in D&D. I think it really worked out very well as a cinematic climax. The book sadly doesn't have anything like that. IMO it really misses the mark there.
Summary
There are four major plot issues that need to be fixed in the book:
Things to do to make this module much better:
If you can do all above as a DM, this adventure is going to be even better than Curse of Strad.
Thanks for taking the time to do the writeup with notes.
Were there a lot of RP opportunities (and bargains) for the characters to engage in once the plot was going? Does it end up being a lot of faction and ally management?
"An' things ha' come to a pretty pass, ye ken, if people are going to leave stuff like that aroound where innocent people could accidentally smash the door doon and lever the bars aside and take the big chain off'f the cupboard and pick the lock and drink it!"
There are a lot of RP opportunities but the plot is still pretty linear. I don't think RP can make any step change to the plot.
There are quite a few factions but there isn't much politics.
It is a very fast-paced adventure, so not much ally management can be done. Most alliances are just one-time deal. You can't really have any long-term trust to anyone in that place.
However, I could be biased because my party doesn't have any bard or rogue. They are an eldritch knight, a gunslinger, a barbarian, a paladin, a bladesinger, and a GOO warlock (yeah, basically 5 warriors and 1 spellcaster, pretty hardcore).