The first product from Mischief, Inc., The Tomb of Rakoss the Undying is an adventure for characters between 4th and 6th level that is written to be compatible with most old school systems. The text doesn't refer to any specific system, but it does include monster stats that, while not exact to any specific system, are written to be reasonably compatible (though they may require some small tweaks) for most old school games. It is a location-based, dungeon crawl-style adventure.
The adventure is sixteen pages (eighteen if you include the front and back covers). There is a Table of Contents that, despite being fairly brief, is perfectly adequate. The Tomb of Rakoss the Undying is, at the time of this writing, listed as Pay What You Want on DriveThruRPG and RPGNow. The PDF is bookmarked for all the relevant sections, but it is watermarked.
After the Table of Contents, the book has an Introduction that includes an explanation of the monster stat blocks, then moves into the Adventure Background, Getting the Players Involved, Default Narrative, and Alternate Plot Hooks. The background includes setting information, though the very next section, Getting the Players Involved, has some advice on how to tailor the adventure to a GM's individual campaign. The Default Narrative section is basically a plot hook and introduction for the players that the adventure assumes is used, though the next section, appropriately named Alternate Plot Hooks, provides some alternate means for the GM to get the players interested in the adventure.
Getting into the meat of the adventure, the next section, entitled Getting There, deals with the party moving on from whichever city or town they start in to the actual adventure site. There's some basic information on an attack on the party from a roving band of ogres, but the details of the encounter (aside from the number of ogres) are left up to the GM. After that follows all the different rooms and encounters that the party may encounter within.
Most of the encounters in the adventure are fairly short, but interesting. The dungeon map is a standard 10-foot grid, and the module also includes a good hex map of the surrounding area (if the GM chooses to use the default module setting). The hex map features mostly terrain features, and is large enough for a GM to add plenty of additional dungeons or other challenges to the area.
The dungeon features multiple secret doors, though how difficult these doors are to discover is mentioned in vague terms like “difficult to discover” rather than explicit numerical values. This isn't a bad thing – it allows the GM to adjudicate for a variety of systems with multiple different methods of finding secret doors.
The necromancer the dungeon is named for, Rakoss, is not present in the module. Rather, the PCs have the opportunity to find a phylactery (which may or may not be real, according to GM preference) that could easily lead to more adventures related to the ancient necromancer.
END OF SPOILERS
Looking over the entire adventure, it's immediately clear that The Tomb of Rakoss the Undying has taken a lot of inspiration from old TSR modules and other old school adventures. The art is good; most of it looks like art that might have been in an AD&D module. Similarly, the boxed text for GMs to read and the simple page styling hearkens back to the aesthetics of classic modules like B2: The Keep on the Borderlands.
Some of the adventure's features are left vague or left to the GM. For a module designed to be broadly compatible with multiple game systems, this is just fine. Specifics like environmental effects on unprotected adventurers are explicitly mentioned to be up to the GM; rather than describing specific effects, this allows GMs to insert weather or exposure rules from whichever system they choose to run this module.
Overall, I would definitely recommend this module to any fan of old-school play or dungeon crawls. The cartography and art is solid, and the writing is clear and concise. The setting information is basic and provides just enough information to give context to the dungeon, while still being open enough for a GM to use the module in just about any fantasy setting. I would give this module a solid 4 out of 5 stars, and I'll be using it in the near future for sure.