If you want to play this one set of rules, check out the following free set at DTRPG. I got the Kickstarter boxed sets a year or two back, and those are not available right now.
You can approximate them with 3 books: The Referee's Advanced Tome and The Advanced Player's Tome, OR you could pick up the digital core book bundle. Again, these are links to DriveThru to buy digital books. These purchases result in remuneration to me.
I wrote a book called Zero to Hero: Uncommon Commoners that covers BX and AD&D NPCs extensively. I am currently rewriting it for OSE. This title is Pay What You Want.
For part one, I don't know how the NPC Generator rolls for stats. Once I post my character sheets, it will become obvious that the stats are out of whack. If I saw a stat of 10 or under, I rerolled it. If I got a score that was higher, I replaced it. But I only tried once. Then I shifted stats around. I didn't honor any rules for doing this; I rearranged the stats as I saw fit.
Then I handed the characters a bunch of cash. I gave them one weapon, one piece of armor, and a backpack full of camping gear. Then I rolled the OSE standard 3d6x10 for gold.
Once the mundane task of acquiring equipment was done, I went through the Treasure books and selected 15 items from the lists. At the front of the list, I selected 5 things I didn't mind having duplicates of, and then repeated those items at the end so that I had an even 20 items. Those 5 items were a Cloak of Defense, a Rope of Climbing, a Bag of Holding, a potion of healing, and a scroll with 3 spells. The list was rounded out with various oddities, like shield +1, armor +1, Eyes of the Eagle, Bracers of Defense, a collection of various potions and rings, and so on.
I rolled 3 times for each character. If I rolled an item that appeared only once, I crossed it out, and the next player to roll that number got nothing. They didn't do too bad, scoring 15 of 18 possible items. You'll notice that I didn't have any magical weapons. That was on purpose; it skews things too quickly in combat at low levels.
On to the actual session. Once I had my 6 characters, I picked 3 NPCs. They were Punch, Rety, and Lefty. I didn't even bother to stat them except for HP and AC. I do love giving NPCs personalities of their own, not so much to harass the players but to make them think.
I wrote a book called Zero to Hero: Uncommon Commoners that covers BX and AD&D NPCs extensively. I am currently rewriting it for OSE. This title is Pay What You Want.
I am vaguely amused when a titled product is subverted by the players. "Dungeons & Dragons: Honor Among Thieves" has no real thieves, the Zoomer in Stranger Things, and this time, a "Keep on the Borderlands" that no one actually stops at. I could see experienced players doing this, thinking they know better.
The next subversion was a road. They could have used it, but made the assumption that a contour line was another road. It worked. It goes exactly where they want it to, but not in any reasonable way.
I planned out the encounter with the Hermit and mountain lion in exactly the way the party was expecting, but they didn't really expect it. I see this as a common trope among players. Let's do something so normal and customary and assume it will work.
All players who use a marching order pack the center with the squishy characters to protect them. Which this ambush didn't respect. The mountain lion was described as being agile, able to leap and bound. Running down the tight space between trees and players is reasonable. And it went right for the 2 people not wearing armor. It is familiar with humans and knows the guys without armor will cast magic.
I have a rule of thumb that was borne out in this scenario. In melee, a creature will last one round for every 3.5 hp it has. And the mountain lion did that perfectly. He was projected to last 4.28 rounds against the party.
On the other hand, he was barely able to hurt one character. But what he did on the way to that goal was a lot. He surprised the rear guard and only got hit once. It foiled an attack by the man-at-arms by spooking the mule. He forced the Cleric to drop his weapon and stopped other characters from shooting into melee. Finally, the lion bit the MU twice before being taken out. That one creature tied up 9 characters for several rounds, allowing the Hermit to kill one guy.
Sure, that last character didn't stay dead, but it counted for something later.
When the party decided to sack down for the night in the Hermit's abode, it forced a morale check. There was no way the NPCs weren't going to beat feet for the safe walls of the Keep. And why not take some treasure for your trouble?
Ironically, that made the NPCs the winners.
