Unhallowed Halls is a rather unusual d20 adventure. Unusual in that it's, to my knowledge, the only d20 adventure set at a magic University. Not the Hogwarts of Harry Potter, it seems a bit more something out of Animal House (or at least far more interesting than the college I went to.) The cover says it's for characters of levels 6 to 8, but the module itself says 4 to 6. It's softcover, 80 pages, and priced at a $16.95. The margins are also quite small, so in terms of text, it's a pretty good deal.
The set up is also a bit odd, but not unique - the characters are invited to a ball (like in a party. If you have players that are AC/DC fans, beware). At least one other d20 module starts off like this, one of the Freeport ones. But in that case, the PCs were invited to the ball because they were heroes of the city, at least temporarily, because of the previous adventures. In this case, it's somewhat tricky to explain why the PCs have been suddenly invited to a ball at a college that never existed in your game world until you bought this book, though several possibilities are suggested.
In my own game, it wasn't too hard to set up, because one of the PCs happens to be the daughter of the mayor of the village the players are sort of based around. So it's relatively plausible that a neighboring town might invite local politicians to a ball like this. But it could be tricky for the average fantasy game...
The adventure premise itself is pretty simple - one of the people at the college is up to no good, and some students have disappeared. (As this is mentioned on the back cover, I don't really consider it a spoiler). For the most part it works, and most of the adventure involves figuring out whose behind the plot. Which is generally pretty simple to do, as lots of potential clues are available.
There's not a whole lot of combat in the adventure. Basically one large combat, and that's it. Lots of roleplaying - talking/listening to people, to figure out what's going on.
I do have some reservations about the main villain's motivations - I really don't see what he gains from his villainous plot. Is it worth the risk? He's got a pretty cushy job. But then again, maybe he has tenure, and doesn't think it much of a risk.
The meat of this product is the descriptions of the town it takes place in, the magical university, and the small village around the university, and the inhabitants of them. While it's not one of those products that describes every single town member, those it does cover are detailed extremely well, which makes them feel relatively real.
I ran the adventure with 6 6th level characters. A 4th level Cleric (plus 2 levels of Half-Ogre), an 2nd Level Ranger/4th level Witch (from Mongoose's Quintessential Witch), a 4th Level Scout/2nd Level Rogue (both classes adapted from Traveller 20), a 4th Level Fighter/ 2nd Level Sorcerer, a 3rd Level Barbarian/3rd Level Sorcerer, and a 6th level Space Marine (a homebrew class, mostly like a Fighter).
Having the Quintessential Witch was a big factor, as they can detect contaminated water. Combat was not a problem for the most part, except the Marine & the Scout/Rogue didn't have magic weapons, only guns, which were more or less ineffective vs. the new monster introduced in the module, the Nightling (they have a damage resistance of 15 vs. non magic weapons).
There's some new d20 material, most notably a new core class, the Mystic. While I really liked the idea of the new core class, it's quite problematic. Why? Well, on first glance, it's basically like a divine version of a sorcerer. Knows several spells per level (from either the Cleric or Druid list), and can cast several spells per day without having to prepare them - similar to the sorcerer's charts, but usually 1 spell more. The basic premise of a divine sorcerer like character is solid enough, and it's actually mentioned as an alternative class in the DMG. But the rest of the class is where the problems lay. They're not allowed to wear armor, which seems something borrowed from previous editions of D&D, but get a defensive bonus, kind of like a monk. They also get 4 skill points a level, average base attack bonus, d8 for hit dice, and have two great saving throw progressions.
They also get a ton of special abilities. Including, which I think breaks the camel's back, from 13th to 20th level, any granted power from a clerical domain (non evil, anyway) that they want. So the net result is a very powerful class. It's somewhat restrictive, which I meant was supposed to balance it, but even so, is way out of line with the regular core classes.
Really, the only bad thing about this (other than the new core class) is that it's skimpy on stats in the adventure itself. It frequently says things like "Use the standard D20 stats" or just gives the very bare bones description of a person, stat wise, just their class, level and alignment. In most cases, there was room for a simple stat block, as about an inch of space is devoted to 1 line saying their class, level and alignment.
Still, this is a pretty major thing. Part of the reason people buy pre-made adventures is because of time. Having to stat all the NPCs yourself is a lot of grunt work. And often how you role-play NPCs depends on their stats, at least the numerical value of things like intelligence or charisma can give you guidelines. In many cases, space didn't seem to be an issue, either, as there was a large about of blank space (for OGL labeling purposes) around the description of a character's class/level.
Of course, conversely, being fairly stat free, makes it more system independant. So while it's for the d20 system, it should work for most fantasy games. The magic of the college is fairly vague, too, and should work with most systems.
Actually, with only little bit of work, it would also work as a scenario for a modern day horror game. The plot would make a bit more sense, too, if the main villain was a Lovecraft style nut-case, and it also solves another nitpicky problem - that of alignment. The main villain in the adventure is Lawful Evil. Now, in D&D, alignment is relatively tangible, you can detect it if you're a paladin or fairly low level spell caster. So people had to know this guy was evil.
The adventure gets a B, the new rules a D+ (The new class an F), and the source material (town, college, thorp) an A. So probably a B+, in total.