I will give my two-cents here on how to use the megadungeon Stonehell Dungeon as “fun-house” for a one-shot game of Old School Essentials. This advice came from my experience some days ago, when I have refereed it for four 1st level characters: in particular, Joyce the Paladin, Doctor the Druid, Smilzo the Thief, and Imowhertheren the Elf. These notes could be useful for someone who wants to use this mega-dungeon as a convention game or online game. I have loved Stonehell as dungeon for a self-contained session: it has all the elements to make experience the old-school gaming to players new to the OSR.
Contains spoilers dedicated to the Referee only. If you are a player, do not read.
My first error has been starting the game at the Floor 0, i.e. the canyon with the gate and the different grottos around the valley. We have spent most of the first session exploring just the entrance. Nice if we are talking about a long-breath campaign, a waste of time for a game that will last only one night. If I had to run Stonehell again for a one-shot, I would make the characters beginning straight to the entrance of the 1st Floor. So, I suggest to start from the first floor of the dungeon and skip Floor 0. Reframe the Stonehell beneath a city or a town just outside the walls. In this way, the characters can stock equipment and supplies, then go straight to the entrance without being bogged down.
My second advice is mixing up the different areas. Put at the beginning advanced sections of the dungeon to spice up the game. In the Introduction, the author suggests treating Stonehell like a toolkit or a framework. I have decided to substitute the Kobold’s Korners (Level 1D) with the Reptile House (Level 2B) — though they did not reach the south-eastern zone of that level during the game. Do not worry to place quarters of deeper levels earlier: facing situations that they should have faced later forces the players to come up on the fly with unexpected approaches.
Third, intensify the presence of the Nixthisis from the beginning. I know that the module encourages to manifest the most obvious effects much later in the crawl. But, anticipating it from the first floor gives a fun feeling of uneasiness to the players. Roll every hour on the Appendix A Chaos Events in the Into the Heart of Hell volume (p. 148) from the start. I love deploying the Doom Lures more often beyond 1C to show the presence of Nixthisis : let the entity hunting down the adventurers actively through its servants multiple times during the session.
The fourth and last advice depends on the taste of the referee: giving a quest or a purpose to the delve. E.g. Saving a priestess kidnapped by the orcs, goblins or the corrupted descendants of the prisoners; mapping the area on behalf of the local guild; retrieving a particular object. This encourages to focus on the most exciting parts of the exploration and negotiation with NPCs rather than grinding treasure. I prefer a pure sandbox style where players do whatever they want in the environment, so I have not applied it; but, some referees would benefit from it to cut dead times and give a pace.