Foul Delvings is a single session adventure for 3-5 characters between levels 3-6 by Josh Kelly.
The characters are hired to investigate a disappearance which leads them to the sewers. What they encounter there is bigger than what they would expect.
The adventure is divided in three parts, which also match the three areas that the characters will visit. These areas are described in much detail. Also, before describing the different parts of an area, environmental characteristics are provided such as light, terrain, odors and sound. This helps the DM understand the area the characters are in and also better convey that to the players.
The second part of the adventure, where the characters explore the sewers, is implemented using an interesting way which adds more randomness. And even if you don’t like randomness, you can use the random encounter table to pick the encounters you want and throw them to the characters.
The combat encounters seem fairly balanced. There’s an appendix which contains guidelines on how to adjust them based on the party’s strength. Also, there are some notes on the tactics of the enemies which I found quite helpful.
I’d like to mention here that there are some devices in the adventure that deal heat damage which is not a damage type that’s included in the core rules. I don’t know why the decision to use a new damage type was made, since fire damage could easily be used here. The only thing that comes to mind is that there could be a reason to make characters with fire resistance or immunity take full damage.
As for the maps, while simple, they cover all the important areas of the adventure and are easy to read.
Ultimately, Foul Delvings is an interesting adventure that can be easily integrated in any city with a wall and a large sewer system. And even if it can be ran as a fun one shot, it provides enough story to create a campaign around it.