Let me say this up-front: I know the author from the interwebs (although not in person) and I’m a fan of his maps and his rules-lite game Edge of Space (aff). I might be a bit biased with this review.

What do you need to know?

Bloodnut Pass is a short old school adventure by Chubby Monster Games/Matt Jackson. It’s written with Pits & Perils in mind but could be used with other games as well.
You can buy it for USD $1 at Onebookshelf (aff).
The adventure is creepy and gross and a bit over-the-top. It is aimed at mature readers. Warning: Spoilers ahead!

Content

With a nod to the animated D&D series the main villain is called Vengar and is an evil cleric who was corrupted by a demon (or is this a stab at Mr. Venger Satanis?). Decades later, what’s left of Vengar is a walking head with spider legs. Creepy.
The idea behind this adventure is that a clan of monsters called Dark Dwellers has taken residence in Vengar’s caverns. They rob travelers, rape, and torture and eat people. Yes, they are evil, no moral gray areas. Generally, this short dungeon romp can be easily plugged into an ongoing campaign. The background is generic enough to fit most settings if you’re willing to live with the weird and creepy. The adventure comes with a small map. The atmosphere of the dungeon is dark, dirty and gross. For example, there is a Meat Locker where the monsters hang the bodies (sometimes alive). I like how this is emphasized by players having to make a save against the foul odor.
Be warned that there is also a Breeding Chamber where the leader of the Dwellers mates with the poor female prisoners.
The encounters are deadly. Especially the leader has the spell STUN which can prove very dangerous to the party.
Vengar can defend himself with nasty insults! Yes, you read that right. His magic affects a PC’s morale which will weaken the character. And he can STUN, too.
Hilariously, the last locations are the Shit Pit and the Shit Slide where characters can leave the caverns. They won’t leave this way without a parting gift: they must make a save or contract a disease. The last section of the book contains the stats for the monsters. The background info is well written. Level, numbers of attack and spells should give you a good orientation on how to convert P&P monsters to a D&D-style game.

Appearance

It’s a 17 pages black & white PDF with single-column-layout. The font style was chosen as a tribute to Pits & Perils and looks like from an old typewriter. While it conveys a certain nostalgic feel it is not that easy to read.
Matt Jackson might be best known for his great old school maps (check out his Patreon). Unfortunately, this map isn’t that good as it uses a new style he is testing out. It’s a bit blurry and missing the sharpness and clear lines I’m fond of.
The interior art is nice. I like the image of the Dwellers, they are very alien and Vengar suitably looks like a creepy fellow.
You can easily print out the PDF as a booklet and the font will be big enough to read comfortably.

Final Thoughts

What do I like?
I’m keen on Pits & Perils and it’s good to see a simple adventure which was written for this ruleset.
I like the image of the Dark Dwellers, they are appropriately monstrous. I also like the humor and the atmosphere of this adventure, but your mileage may vary. What I would have liked to see?
Just for convenience sake I’d like to have stats for Swords & Wizardry or Labyrinth Lord. Some P&P entries are a bit cryptic without having the core rulebook. And please give me those nice maps you normally do, Mr. Jackson! Musings
I find this adventure difficult to rate. While it is solid work it is not necessarily a must-buy. It’s a small dungeon romp good for a few hours of gaming.
The tone won’t appeal to everyone. Especially the Breeding Chamber and the Shit Pit with the remains of those experiments could be upsetting for some players.
Furthermore, it’s a bit wacky. But I like it. It’s a decent adventure and a fun read and I would GM it.
Bloodnut Pass will come down to personal taste. I’d guess that you’ll either like the premise or you’ll think it is ridiculous.

Links:
Bloodnut Pass (aff) Chubby Monster Games/Matt Jackson Pits & Perils (aff) Edge of Space (aff)