The Goodman Game's versions of B1 and B2 is a really cool book, huge is one way to put it, with a full reprint of the basic module plus a 5E update of the same. You get all the maps, plus the 5E versions of the adventures are expanded and statted for that rules set.
And I played it as a part of a Pathfinder 1e game recently. I used the old-school module and converted up to Pathfinder, and skipped the 5E version.
Let's say, my experience was definitely old school, but not the type of old school I like. Going into the kobold lair, killing the guards, having a swarm of rats attack, and then holding off a hallway where charge after charge from the kobold's living area fell in piles in the hall felt...it felt wrong.
Not heroic. It felt like invading a tribe's home and killing them all because they have loot. We ended up a bit shell-shocked after the battle, and it felt really scummy for all involved. Like the party did something wrong, and my players felt that as well.
Wait, aren't we supposed to be the good guys here?
The Kobold Insurgency
We had a random event I rolled for later, and I ruled because the kobolds were attacked this way, the local tribes banded together and formed a "kobold insurgency" in the area and a general war broke out. It didn't make the party feel any better, and they knew they caused it, but it kind of put a bookend on a really ugly feeling encounter we had there.
But ugly encounters happen, and not every fight can feel heroic. I know and so do my players. This is the hardships of being an adventurer, sometimes bad things happen and you deal.
And this reinforces the idea of consequences outside the published module in the game world. You tip the cosmic balance and there is a possibility of a reaction happening. And here, one did.
And it was fun bringing up the insurgency every now and then as the kingdom battled it, the checkpoints, the fires in the hills, the soldiers marching out to the mountains, passing burned out farms, the town criers announcing wins and losses in the campaign - it became a fun backdrop to the game and the players enjoyed knowing the mess they made had a larger impact - although one where if it never happened none of this would have ever began.
But perhaps it was destined to all along.
And no, they did not tell anyone of their involvement. It became a sort of open secret to the party, and with each random event tied to the insurgency they knew they would have to go out there and end what they started.
But, what was wrong with us?
Back when we were kids, yeah, they are all evil, here is a room full of them! Yeah! Blast them like a hall full of creatures out of the Gauntlet video game and grab their loot! The modules of those days were simple, room X filled with monster Y sorts of places, and just having a map with keyed rooms was cool and saved us a lot of work.
And I am not dumping on this module, the Keep on the Borderlands, my brother and I loved this place and had our first campaign here with characters that lasted for 40 years. This is where it all began for us, and I still have the home-made maps we made with graph paper and coloring pencils.
But I guess my tastes changed. I like stories, plots, and adventures now. I don't want to go in a hole in the ground "just because treasure" and kill everything down there for XP and GP.
Yes, the kobolds are technically "evil" in this module, it is assumed, but with no support or trappings like demon statues and the like, it felt wrong. I helped rectify that by making the united tribes evil and despicable during the game, so it sort of balanced out.
It would have helped if the original module eliminated the non-combatants and painted the tribe as evil raiders with loot gathered from raids on innocent villages, then the raid would have felt justified. Perhaps this was an oversight on my part, but I was running the module as-written to give them that experience, so this I felt was an interesting topic to write about.
To Be Fair...
The 5E material was excellent, and pointed out some of the problems of the original adventure. The criticism of B2 being a "monster hotel" was correct and a fun admission of the original material's shortcomings. They did try to fix a lot of the issues in the adventure, provided better descriptions and updated encounters, and I wished I would had started with the 5E side of the adventure before I put it aside for the original version.
The 5E material also mentioned when the group would surrender, and clearly laid out non-combatants (and did not stat them), so a more modern sensibility and adventure designer made some great tone choices here. I never likes the classic modules giving hit points for younger non-combatant monsters (or even mention their presence), it just felt wrong to put players in that position where they could accidentally injure younger members of the tribe with a misplaced oil flask or fireball. Let those on the map be combatants and leave those there as the ones responsible for evil occurrences.
There is also a reasoning why the monsters are all here, something to do with the chaos altar present here that draws the monsters to this area despite their antagonism and differences. It is a weak reasoning to hand-wave and say 'because magic' but it is something I could have worked with if I had wanted to. There is a difference between running the old adventure as-is, versus having the kobolds aware of a mind-altering presence in the area of "evil magic" and having that affect their actions.
The party could see a group of kobolds not attack a bugbear because some dark magic willed them to, and that would have aroused suspicion and played into that overall story arc of this place. Once the altar of evil is destroyed, the Caves of Chaos would be as well, and the party could have a sense of accomplishment within a larger narrative and the monsters could go back to being monsters.
I give the 5E section props (and one which I wish I would have read a little more before I ran this), and the tone change between expectations then and now is one thing to be aware of when running older modules. I know, it should be apparent, right? Not all the time, and in this case I stepped on that rake and it hit me in the face.
Turning it Around
By the end of the game, the insurgency did come home to roost and they got drawn into the fight and helped end it. It did sort of put an end to what the party started, and they felt they had corrected a mistake - that wasn't really a mistake because the module was written in a different time and expected a different type of player - one more interested in math and loot than story or plot.
It was a strange situation where and old-school module met modern sensibilities and a desire to play more plot-based games, and I refereed it as having a real consequence that became a backdrop and end to the game. They had fun and we talked about our feeling afterwards, and everyone agreed the insurgency was a fun way to take what felt like a morally-dark old-school slaughter into a larger story and they thanked me for turning what was an ugly situation into something they didn't like having to fix, but they did anyways because they felt responsible.
I pointed out that the situation was likely a powder keg likely to go off not maybe by this, but something else, and they understood and agreed. It was turning lemons into lemonade, but it made sense of something that felt wrong in the beginning and provided closure for the group.
I would make this an adventure location with a reason for coming here, not just to clean the place out, but a kidnapped merchant and a rescue mission, or some other plot based reason to be here, get in, and get out. This would go from a "clear out rooms 1 to 100" sort of game to a adventure setting that serves as a background for a larger story. Not a place to clean out, but as a set where larger plots and stories happen.
Then again, is it a great setting for that sort of story, or is this just fan service? Again, I am struggling. No, realistically, you would not have so many tribes - some hostile to each other - within walking distance of each other. They would not walk out of their caves every morning, punch their timeclocks, and say "hello Bob" and go off to raiding and looting only to come back here later to live in a small, easily accessible, openly known about hole in the ground when they have a whole wilderness map to go make a camp or fortress in.
And when you think about it, the larger and stronger tribes would have wiped out the smaller ones years ago and taken their stuff, perhaps collapsed their caves, and left to go find somewhere more secure, private, and defendable.
And next time, yes, I will be smarter and start with the 5E version with the tone fixes and updated content. I can still swap monsters to whatever system I am playing, but it helps having the fixes and additions to consider.
The Forbidden Caverns of Archaia
Yes, I know B2 is a classic and near and dear to the hearts of many, but I need to mention the Labyrinth Lord module of The Forbidden Caverns of Archaia. This is a way larger experience, but conceptually the same, and a bit better constructed. If I have a "goblin lair" or a "kobold lair" map that out as a standalone, and put it on a larger "adventure area" map (or let the DM place it somewhere), and then you can have a "Caves of Chaos" style area without having it feel too cramped or connected.
The bonus to this type of approach is you can create a classic experience, such as a kobold lair in the ruins of an ancient serpent cult temple, and have the room to create secret ways in, story and plot hooks, and even lost areas where remnants of the old serpent cult may still be around.
I prefer this style of setup to B2's, and this feels much more sandbox and open to me as a referee. The tribes of monsters have room to fight, skirmish, patrol, grab territory and resources, and retreat back to their defended camps and homes to plot another way to rule the lost valley where ancient power lies. Outside tribes could be called in as the war escalates. The players could pick a side, or their actions weakening one side or another could tip the balance of power and cause unforeseen consequences.
And you can ignore or move things around if you want to focus on one group of bad guys. You are not limited by the classic map's tight layout and structure. I would have liked the 5E adventure to space things out a little more with a larger adventure area and sites farther apart, but it is what it is. Messing with a classic that much would have been likely controversial.
In this sort of a "area map plus locations" setup there is more room for player agency and choice. If the story goal is a kidnapped merchant by one of the tribes, getting in, doing the rescue, and escaping are clear goals and you aren't "clearing a map" and you are not forced into areas that have nothing to do with the story.
A Great Book
Despite our strange play experience, I love the book and the work they put into this, and I am planning on getting the others in the series (and I hope they do the Slave Lords "A" series someday). It is clearly a labor of love with interviews, expanded material, a 5E conversion, and plenty to do. Highly recommended, but make note of some of the old school expectations and assumptions and feel free to wrap this into a larger story of yours that changes things up and makes "clearing the map" not the primary goal of the story or mission.
Then again, if you are just going for the old school feel with a modern rules set, dive in and have fun.