Out of the Abyss expected levels?

[Grod_The_Giant]

I've recently started DMing Out of the Abyss, and I'm... not entirely satisfied with how it's structured. The first couple chapters post-escape seem pretty sandbox-y, which is fine... but there's no indication of what areas are appropriate for what level party. I've heard "about one level per chapter," which would leave you at the appropriate level (7) when you reach the surface and things get more linear, but do the chapter numbers roughly correspond to that?

For example, if the party decides to head straight to Blingdenstone, do I need to sidetrack them before they run into an adventure aimed at 6th level characters? Do I need to keep the Sloobludop/Gracklestugh/Neverlight/Blingdenstone order?

What I'd really like is something like the table in Curse of Strahd that said "the Wizard of Wines is approriate for 5th level characters, Vallaki for 4th..."

[Unoriginal]

None of the area are level-dependant. It is, as you said, more of a sandbox, which mean that sometime the PCs will walk in on major threats and other times the challenges will be easier because they're of a decent level.

In other word: don't try making things level-appropriate. If they try to attack a CR 12 demon at lvl 3, it's up to them.

If they decide to run straight to Blingenstone, you don't have to sidetrack them, but you could provide incentives for not going there straight up (ex: meet someone from one the other locations on the road who can reward them if they do the detour). It's important they have the choice, though.

[Legendairy]

The order can be mixed up a bit, blingdenstone and the escape at 6ish is what I did. The drow they have to face are tough. You can look at the monster stats in each area and get a feel, but I would gauge on that. I will admit at times it felt odd awarding a level because it didn’t seem like the group accomplished a lot but I knew the plans of where they wanted to go next. If you are struggling for them to be there throw in a few smaller planes randoms. I don’t remember the order my group went but they chose blingdenstone last luckily. I think they went from sloop to gracklsaugh to the myconids, it’s a bit fuzzy tho. The level a chapter seems ok to me but I’m not looking into the book right now. I would gently nudge them away from trying to exit until they can hold their own against the ooze kind and the drow.

[Grod_The_Giant]

None of the area are level-dependant. It is, as you said, more of a sandbox, which mean that sometime the PCs will walk in on major threats and other times the challenges will be easier because they're of a decent level.

In other word: don't try making things level-appropriate. If they try to attack a CR 12 demon at lvl 3, it's up to them.

If they decide to run straight to Blingenstone, you don't have to sidetrack them, but you could provide incentives for not going there straight up (ex: meet someone from one the other locations on the road who can reward them if they do the detour). It's important they have the choice, though.
Oh, sure. I'm not going to stop them from doing something stupid, but I'd like to know what to expect as a DM, so I can drop hints that an area is going to be overwhelming before I start setting up a combat after two hours of roleplaying and realize "wait crap, there's ten of these guys and they're CR 3?"

[Unoriginal]

Fair enough. In that case, IIRC (as it's been a while since I've read it and never in-depth), each area has mixed-CR encounters. My advice is to calculate the CR of each, maybe with an online tool to make it speedier and easier.

IMO, though, part of the fear factor of the Underdark is specifically that you may spend 2h roleplaying, but when it comes to fight you may have to run for your life.

[Legendairy]

I also think there is a chart that talks about what level they should be when they approach certain areas/chapters. I don’t recall exactly where it is in the books.

For the first part just keep adjusting, also remember the slew of NPC’s to help offset some of the encounters.

[Grod_The_Giant]

I also think there is a chart that talks about what level they should be when they approach certain areas/chapters. I don’t recall exactly where it is in the books.
A couple chapters mention milestones, but between "lv 2-3 after escaping" and "lv 7 when leaving the underdark" I can't find anything.

[Legendairy]

Qaugoths, cave crickets, nanny plunk, and whatever else you deem worthy and fun for your group, it runs pretty smooth. If I recall right, you posted a while back about using the npc’s as boosters and not playing them, I don’t know how they effects the groups CR calculations. I ran them all as individuals, had cards with accent, personality, key features, and combat stats. I didn’t over worry about TPK’s or them reaching beyond their bounds, the npc’s deaths meant a lot to them and also signaled that the fight might be a bit much for them.

[Dudewithknives]

The book is not set up very well, honestly.

The whole section on the deep dwarf city, whatever it was called, is horrible to keep track of.

[SunderedWorldDM]

I'm running now, here's how I'm doing it (I use milestone, not XP):

1) Escape Velkynvelve
2) Wandering the Underdark to Sloobludop
3) Escaping Demogorgon's destruction of Sloobludop, interacting with Gracklstugh
4) Clearing the Tomb of Khaem
5) Clearing Whorlstone Tunnels
6) Neverlight Grove
7) Blingdenstone

Haven't planned that far ahead, so this might change. I also homebrew quite a bit, so my campaign's highly irregular, but heer's the current idea...

[Legendairy]

I'm running now, here's how I'm doing it (I use milestone, not XP):

1) Escape Velkynvelve
2) Wandering the Underdark to Sloobludop
3) Escaping Demogorgon's destruction of Sloobludop, interacting with Gracklstugh
4) Clearing the Tomb of Khaem
5) Clearing Whorlstone Tunnels
6) Neverlight Grove
7) Blingdenstone

Haven't planned that far ahead, so this might change. I also homebrew quite a bit, so my campaign's highly irregular, but heer's the current idea...

Basically how I ran it I think....the campaign lasted about a year and a half or so, please forgive me if I don’t remember the details. And it was about 2 years ago.

[Gastronomie]

In my case, I simply told my players through my NPCs that the best route to Gauntlgrym is via Sloopdulop > Gracklstugh > Neverlight Grove > Blingdenstone. I found it better that way, since I can prepare stuff more efficiently.
　
I also ignored a vast majority of the original book including the terribly done chapters and random encounter tables (which I have never trusted), setting up each encounter as an original one every time. It does take some effort, but it works better for me. (One reason I was capable of doing this was that Chapter 2 provided a lot of ideas for me with terrain and such.)

As result it's now something completely different. I view this book as a "really well written setting guide to the underdark infested by demons", and use it as such.
As a scenario book? Not so much.
(ppl from my table, please don't look, though I doubt you guys will)

I spiced up quite a lot of the campaign with original ideas. The original one seems a bit dull for me.

At my table, Buppido was an Avatar of Orcus who, after murdering a PC and going back to Gracklstugh, became the leader of a Derro organization plotting revolution against the Duergar. He proceeded to become the big boss of the chapter as a much beefed up necromancer, his goal to turn Themberchaud into a dracolich in order to destroy Gracklstugh completely. Demogorgon's influence was scrapped from the chapter since I found it redundant.

Neverlight Grove is terrible because it shows no way to help the village the first time the PCs get there. At my table, I made it so that the time the PCs get there it's already explicitly overrun by demons, but I had a Society of Brilliance member tell the PCs it's possible to find hints in the Stone Giant Library and had the party go there, where... they find out that the way to heal the madness of the villagers is to utilize the power of the Maze Engine. (I know, it's a bit of a long way around.) At my table the Maze Engine is less "what the hell is this even for" and more "this is the key to restoring peace (sorta; it's not like it was a safe place from the start) in the underdark". Here they obtain crystals that can heal demonic madness and greatly weaken the power of the Demon Lords, which is my way of explaining why these overpowerful entities' CR is about the same as a dragon. Right now my party is around here.

Blingdenstone will not be about a battle against oozes, because (i) just oozes are dumb, and (ii) I wanted Graz'zt to take an actual role in the campaign. In my campaign Lolth has completely trashed the FR drow and is now ignoring their pleads and voices, thinking it's impossible for them to survive the demonic invasion. However, Graz'zt has saved and taken control over the drow instead, one because they make good minions, one because he just wants to piss off Lolth, and one because drow females are pretty darn sexy.

Since Menzoberanzon is already completely destroyed by the demon lords (why the hell is it still intact in the book?), the drow need a new place to live. They invade Blingdenstone, and the PCs have to deal with it.

Since I don't like the idea of going to the surface once and going back down again, I will have Vizeran show up in the Blingdenstone chapter and rush to the ending.

I know, it's completely different.

[Legendairy]

I live the content of the book for setting up the underdark, it has some good things. I took a lot of liberties with the module and I do not use random encounters, ever. I always plan the smaller encounters and they are all there to drive the pace, while some feel random they are designed and have reason in the world, the reason may not come up but it’s there.

[Cwyll]

agree with above; my groups now heading for neverlight and are level 6. Then it's Blingdingstone at level 7 and out.
They did get overloaded in Gracklestug and bugged out fast, so didn't pursue any of the big plots there, so 'might' go back on behalf of the leaders of Blingdingstone.
I expect they'll just go for the surface however and move into the more linear part 2 of the book.
Final goal of level 12-15 for the ending.