I've been running a campaign of PotA for the past 2-3 years with a group of 7 PCs. Yeah, it's taking a while due to the large group size and life realities that sometimes keeps us from having a session for months. Anyway, I see the light at the end of the tunnel, and I've asked them to think about what they'd like to do when this adventure finishes. They all voted to keep playing the same characters together in a high-level adventure!

So now I'm trying to figure out where to send them. I don't have the time or ambition to home-brew an adventure, so I'm looking at what we already own in my D&DB library (Legendary Bundle.) Tomb of Horrors seems to fit the bill, but I can't determine what level(s) that dungeon is meant for. I expect them to finish PotA at level 13 (14 if I let them ding when they complete it.)

Based on my initial perusal, ToH seems less combat-focused and more of a thinky type of adventure of solving problems and avoiding traps. Am I in a world of trouble trying to run 7 PCs through ToH, or is this a good follow-up adventure for them?

I haven't tried to run the Tomb of Horrors yet but I have researched some of it. One thing to keep in mind is that the Tomb of Horrors was originally designed by Gary Gygax specifically to kill powerful player characters. So it's tough. At least some of the characters will probably die. That being said, playing Tomb of Horrors seems to be a rite of passage for D&D players. So it should be fun but make sure your players know that their characters are a serious risk!

Well, I don't think the risk is the issue. They've cake-walked through most of PotA even after I adjusted encounter difficulty to match the party size. Every time I think I've got them on the ropes where they actually need to worry, one of them has a brilliant idea/work-around I didn't think of, and I wind up handing out Inspiration rather than beat-downs. But they really do seem to enjoy the sessions where they truly feel at risk (even if they weren't.) So I think they would enjoy the challenge of ToH.

My primary concerns were:

A. What level should they be when they enter?

B. Are there any milestone points in ToH where they should be gaining levels? And if so, what level do they need to be for the final encounter?

I want to make sure I give them a fair chance. If they think it through (it's a group of smart people) they should succeed because they were smart. I don't want them to fail because they thought it through, but were under-leveled which isn't their fault.

You could run a couple from Tales from the Yawning Portal.

Against the Giants (would need to be scaled up a bit for level 13 since it is aimed at 11-12)

Tomb of Horrors ... (I don't have personal experience with this one ... but I have heard that one of the reasons for its reputation are the traps ... if your players aren't thrilled about traps you might want to read it over before running it).

However, since you are looking at Tomb of Horrors ... Dungeon of the Mad Mage could provide you with a lot more level appropriate content (though it is all still dungeons). Level 13 to 23 of the dungeon are designed for level 13+ to level 20 characters. So that might be a better source of pre-generated content. Potentially, you could place the different dungeon levels in different locations or link them together with whatever storyline makes sense to you in case you don't like the existing storyline or it doesn't tie in well to your current campaign.

Tomb of Horrors would be a cakewalk at level 13/14. They will only be in danger if they're careless on purpose. At that level you have to give it an effort in order to die.

A good challenge would be level 8-10s.

There will probably NOT be enough content in the dungeon to gain them a level but they will get a decent amount of treasure.

** side note. ** Make sure they either have a magic ring or give them a magic ring early in the dungeon.

After they blow up the spooky skull, you can send them at Against the Giants. Same source book. It says lvl 11 but you might have to bump the encounters a little bit.

Quote from David42 >>

... Dungeon of the Mad Mage could provide you with a lot more level appropriate content (though it is all still dungeons). Level 13 to 23 of the dungeon are designed for level 13+ to level 20 characters. So that might be a better source of pre-generated content.

The only problem with this is another member of my group wants to DM the entire Dragon Heist/Mad Mage campaign. So I won't steal part of Mad Mage for this campaing.

Quote from Wysperra >>

Tomb of Horrors would be a cakewalk at level 13/14. They will only be in danger if they're careless on purpose. At that level you have to give it an effort in order to die.

A good challenge would be level 8-10s.

There will probably NOT be enough content in the dungeon to gain them a level but they will get a decent amount of treasure.

** side note. ** Make sure they either have a magic ring or give them a magic ring early in the dungeon.

 

Quote from Wysperra >>

Tomb of Horrors would be a cakewalk at level 13/14. They will only be in danger if they're careless on purpose. At that level you have to give it an effort in order to die.

A good challenge would be level 8-10s.

There will probably NOT be enough content in the dungeon to gain them a level but they will get a decent amount of treasure.

** side note. ** Make sure they either have a magic ring or give them a magic ring early in the dungeon.

 

Quote from Wysperra >>

After they blow up the spooky skull, you can send them at Against the Giants. Same source book. It says lvl 11 but you might have to bump the encounters a little bit.

This is the first time I've heard of anyone being over-leveled for ToH. Most things I've read is it can be deadly even to higher level characters if they aren't smart or get unlucky. Unfortunately, I don't want to drain levels from their characters, and they've already stated they want to continue with these characters instead of starting new ones.

What magic ring are you referring to?

I'll look into Against the Giants, but the reason I didn't want to home brew is the extra time needed. Having to re-balance every encounter to accommodate higher level characters doesn't seem much better.

Quote from Wysperra >>

Tomb of Horrors would be a cakewalk at level 13/14. They will only be in danger if they're careless on purpose. At that level you have to give it an effort in order to die.

A good challenge would be level 8-10s.

There will probably NOT be enough content in the dungeon to gain them a level but they will get a decent amount of treasure.

** side note. ** Make sure they either have a magic ring or give them a magic ring early in the dungeon.

 

 Really? I think that ToH would probably still be difficult at 20th level. So much rides on perception and slight of hand checks, and if you fail those, you will fail the adventure. As well as the large number of instakill effects.

I made a post about the tomb a long time ago and I can't find it.

The sliding block entrance asks for an initiative roll. At that point the party knows something is up. Easy to avoid.

The falling rubble trap does little damage.

In the back of beyond, nearly every trap was possibly lethal. The pits had save or die poison. Now they're save or take half damage poison. Same for the door spikes. Not to mention that some of your PCs might be immune to poison at this point.

Before: The Sphere of Annihilation would just kill you. Now you just take 4d10 damage. But who would be stupid enough to stick a body part in there in the first place?

Every monster in the tomb has been nerfed heavily. The skeleton would be a challenge for lvl 8-10 but a single target against 5-7 lvl 13/14? It will die in 1 round.

Gargoyle, Ocre Jelly, Animated Swords, pft.

The sliding hall into death inferno requires the party to be stupid.

The blood door and juggernaut could present a problem. Give those some thought but none of my groups fell for them.

 There is no level draining in the dungeon.

The ring is REQUIRED in order to progress in the dungeon. If they don't have one, they can't get the end. 

Demilich. Previous version was very dangerous. If your party wasn't set up specifically to kill the thing, you would die. Each eye and each tooth would eat your soul turning you into slop. No Save (2 eyes, 6 teeth). Only weapons of +4 or better could hurt it.

"only a fighter with a vorpal blade, a ranger with a sword of
sharpness, +5, or vorpal weapon, or a paladin with the
like or even a +4 weapon can inflict damage upon the
skull."  - Tomb of Horrors p. 10

That is pretty darn specific. And only a handful of spells could hurt it.

Now it's just a monster that can't move (only hover) that has 20 AC and 80hp. Your party can do that kind of damage in 1 or 2 rounds no problem. At lvl 13/14 your players should be have magic weapons and be smart enough to NOT use necrotic, psychic, or poison against undead.

The howl oooooohhhh Is range 30 Con 15 save or 0 hp. not Dead, just unconscious.

Trap Soul. The demilich targets one creature that it can see within 30 feet of it. The target must make a DC 19 Charisma saving throw. On a failed save, the target’s soul is magically trapped inside one of the demilich’s gems. While the soul is trapped, the target’s body and all the equipment it is carrying cease to exist. On a successful save, the target takes 24 (7d6) necrotic damage, and if this damage reduces the target to 0 hit points, its soul is trapped as if it failed the saving throw. A soul trapped in a gem for 24 hours is devoured and ceases to exist.

If the demilich drops to 0 hit points, it is destroyed and turns to powder, leaving behind its gems. Crushing a gem releases any soul trapped within, at which point the target’s body re-forms in an unoccupied space nearest to the gem and in the same state as when it was trapped.

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Yeah, that could ruin your day but the party will win so getting new bodies will be the only problem. 

You could also try Tomb of Annihilation. I haven’t played it, but I’ve heard it’s a really good high level dungeon crawl with some wilderness stuff too.