D&D 5E How challenging is Out of the Abyss?

I just finished reading my copy, and I'm concerned that the later half is going to be rather easy for characters of the designed levels. The major issue that I'm seeing is that most of the fights that you are actually likely to get into (I'm assuming you aren't trying to launch an assault on a noble house in Menzoberranzan, for instance) just don't have enough enemies. Either you are squaring off against a single powerful opponent (maybe with one assistant) or you are fighting a random encounter that is probably going to roll less creatures than PCs (especially if they are powerful enough to be an interesting fight).

Having just finished up running my players through the overland of Isle of Dread--even integrating my own random wilderness encounters into the ones included--I've determined from experience that the 5e wisdom I always agreed with on principle is true: you must outnumber the PCs to have a challenge*.

Numbers of opponents seems so much more important than CR of opponents, that a few dozen goblins with bows might be more of a threat than a couple of trolls (unless you can drop a well-placed area of effect). A party's ability to deal death and destruction with focused fire is just that good.

How have your experiences with the challenges of the second half of Out of the Abyss been? (I'm not focusing on the Demon Lords here--since mine will be upgraded and have high level demon lieutenants.)

* Or pit them against something way above their normal challenge range, in which case you have a different problem--that the party can still probably take it out in a few rounds, and the question is whether someone gets unlucky and dies along the way.

My players found 90% of the combats too easy and the other 10% were nearly TPKs.

Especially the first levels are far over the top, it is hard for some groups to realize that

Spoiler















They need to run at some point
Do not reply directly to this post, please, since I play oota atm and do not want to get spoiled.
I only read the thread headline also, for this reason.

We were trounced in the very beginning, fleeing in the Underdark. No oone had darkvision.

Deleted,

I run the campaign when it came out. The first half was hard, but not only taking about combat. Starting with no items and trying to escape is not easy. Dealing with underdark wilderness is not easy. I used the mad npcs to spread chaos on the pcs. But after the first half the party was completely lost, one of the players told me his character just wanted to have a tomato farm... At the end there was a tpk with the zentharim because the toxic player insisted in bullying the beholder.... So that's my experience.

It depends on the DM. I ran it out of the box the first time, as written. The first half was a challenge for the group. The last half was a breeze. They ROFLStomped DemoGorgon in the last fight; poor rolls and poor action economy. He didn't last long at all.

The second time I ran it, I took the lessons from my first go around. I kept the first half as is, and it was still a good challenge. The second half, I adjusted significantly. And in the last fight with Demogorgon, I gave him full hit points and let him have his legendary actions (which goes against the recommendations of the module), and the fight was much more intense and satisfying...it ended up being a running fight through the streets of Menzoberranzan as the party played a game of cat and mouse with the demon lord, doing guerilla ambushes and then running and hiding as Demogorgon tore down buildings in order to squish the little bugs.

I ran Out of the Abyss a few years ago. The first half (level 7), solid. The 2nd half, totally wrecked. There's nowhere near the encounters to reach the suggested levels. It's like they gave up and hoped you'd fill the void with random encounters (hundreds of them).

So yeah, the battles are really out of sync with suggested levels. Even so, it's clear they didn't have a strong grasp on how powerful characters get at 9th level and higher. I'm convinced, and others have described, a 12th level party could easily take out Demogorgon.

In the end, I used milestones and maxed the party at 14th. In retrospect, I should've stopped at 12. I also ran the suggested "grand melee," letting each player assume a demon lord and battle it out, then the PCs faced down the survivor. Off topic: had some players who created terrain for me, printed some 3-D demon lords. Was an epic finale.

Finally, I buffed my demon lords. Heavily. There's no way a group of mortals who were 1st level a few months ago should be smacking around an eons old demi-god with spell casting worshippers like it was their little bitch. Part of the buffs included:

• Max hp
• Immune to nonmagical damage, resistant to weapons under +3, full dmg from demon lord natural attacks
• More spell-like abilities drawn from their 1st edition manifestations.

This made even a heavily wounded demon lord (our survivor was Yeenoghu in an upset) a nasty terror. Another in restrospect: the party had a wand of magic missiles and used it to bypass all the resistances, just burned the thing down. In retrospect, I might have also buffed demon lords with Rakshasa-like magic resistance. Again, many of these beings are near-gods. They need to look and act like it.

I found that the challenge level remained pretty manageable throughout, with a few exceptions. I did alter and increase the numbers for some of the battles as needed.

I'd say only a few of the encounters were skewed - the Pudding King, in hindsight, should've been way buffed up (though it was funny seeing this gloppy gnome-ooze calling himself a King get taken down so quickly), while Zuggtmoy was a fight that had me worrying that we were going to be looking at a TPK by the end.

Demogorgon didn't kill anyone, though it came close for a few of them, and the fight lasted for hours.

But it also turned out that one of the players was cheating like a fiend (he is now no longer in the group).

Thanks all, that's about what I was expecting. Hmm. I use very slow advancement rules so this adventure is just going to be inserted, in two parts, into a long campaign with other adventures. I was considering running the first half at around level 7, and the second half somewhere between 12-14 (assuming they'd gain one level during it). I was already planning on buffing the demon princes and probably making demon encounters in general more believable (ie, instead of 1d4 X demons, have 2 or 3 different types of demon per encounter), as well as integrating the random encounter tables in the book with my more detailed ones. However, the relative weakness of the rest of the adventure (and I don't arbitrarily buff stuff that doesn't make sense to in the world) makes it a bit tricky to figure out how to fit it all together. I might just have to balance for the final battle and let the party walk all over most other things except for an occasional challenging random encounter.

I suppose I can find that balance point the hard but kinda fun way: mock battles. Take the PCs (I always have a copy of their character sheets, though more to make sure they don't forget their own features than to guard against cheating--I have honest players) and face them off in a battle against the monsters, playing them effectively using the sorts of tactics I've witnessed them using before. Repeat a couple of times.