The Black Wyrm of Brandonsford is, well, an excellent OSR adventure, and you should probably stop reading now, click on the image, and buy it straight away.
As I'm writing this, it is even part of the GM's Day Sale at DriveThruRPG...
- Number one, everything connects with something. The NPCs in town have their hooks and miniquests and information bits that may lead the adventurers in new directions, look for certain areas, investigate places, and so on.
- Number two, freedom. There is nothing the group has to do in order to "solve" the scenario, but there are lots of different paths of action that can make the battle against the dragon much easier. Even the "miniquests" are great, interesting situations with no predefined solution but a variety of possible approaches and outcomes. Everything is open-ended, but tightly designed to push adventure on.
- Number three, great formatting and text. As far as I'm concerned, they're pretty much perfect: sweet and short and well organized, without useless fluff. In just 18 pages you get hours and hours of gaming, and they're very easy to understand and prepare thanks to a clear layout and use of bold and bullet points.
- Some creatures don't have their stats in the adventure: I remember the fauns and the witch, not sure if that's all or I'm forgetting something. This is solved with using stat blocks from your game of choice. And if doesn't have them, you can just wing it using the gnoll stat block and a level 4 magic user, I guess! For Old-School Essentials, you have Satyrs in the Advanced Fantasy monsters book, but no witches it seems!
- Exploring the outdoor area, and familiarizing with the town and the locals is intentionally left to the GM. This means you must think how to start the scenario and run the exploration. Luckily, you may use these maps I've found on Reddit: hex map of the area, and Brandonsford town map, both by Bricky (reddit user BadRussell). Oh and there's also this colorized map on Imgur.
- In the goblin castle map, number 3 and 4 are swapped; and so are 10 and 11 in the Barrow Mound. This was pretty obvious from the room descriptions.
The Black Wyrm of Brandonsford is an excellent OSR adventure, and you should stop reading now, click on the image, and buy it straight away.