The plot is interesting, engaging and pretty nice for a set up for a getting the PC's deep in the action Wiki has a pretty good overview of the adventure plot ; The scene of the action is Guido's Fort, located at the end of a road, with only the River Shrill, a mile wide, separating it from "The Hill". At the Fort, hardy bands of adventurers gather to plan their conquests of The Hill, the hulking mass that looms over this tiny settlement. They say the Hill is filled with monsters, and that an evil witch makes her home there. No visitor to The Hill has ever returned to prove the rumors true or false. Only the mighty river Shrill separates the player characters from the mysterious mountain." But the first thing that the PC's are going to run into is a mess of hobgoblins and goblins. Jim Halloway's hobgoblins are different then many dipictions I've seen and have a Morlock quality about them.
The module is well done but there are certain adventure plot element problems. There are some big problems right out of the gate, the module is trying really hard to use the standard alignment of OD&D to justify its own monster, encounters, NPC's, and plot elements. All roads lead to the boss monster at the end of the module, this is a very nasty bit of business and a problem because it makes the PC's confront the monster eventually regardless of their actions. Too much lame treasure being handed out to the PC's and not enough mystery within the adventure's bounds and setting material, this is one of those treasure equals experience points adventures that were going to become more common as time went on. Yeah, so its a bit of a railroad and has some minor issues. But the pluses far out weight the negatives in this adventure if your willing to look. According to Wiki; "The module contains around 20 encounters on the surface, a monastery, three dungeon levels and three new monsters." Believe it or not this is actually a really brutal adventure that can and has wiped out a number of parties that I've run through.
There is a terrific feeling of being trapped in a hellish fairy tale or dream like atmosphere in B5, but it seems to be lurking in the background of the adventure. You've got factions of neanderthals vs ogres, hobgoblins lurking in the background waiting to pound PC's, witches cutting deals with PC's, a strong sandbox feel to the whole setting, and a massive horror waiting on the Hill itself. Then there are a ton of other classic adventure elements plus dungeon crawling, high weirdness, and lots small side bit quests, encounters, and some interesting ideas. Pull all of that forward and run this as pulp driven sword and sorcery adventure, all of the elements are already build into the background of B5 The Horror On The Hill. There are some great ideas for a complete reskinning of the module over at Dungeon of Signs.
I love a ton of the ideas that he's done with B5 and they're fantastic but I did something a bit different with Horror on the Hill. I upped the sword and sorcery elements and set the entire adventure within the confines of Hyperborea. I left the dragon as is as a one off, changed around the humanoids, left the neanderthals and had the events of the module taking place within a cross road point between the PC's homelands.
This option worked pretty damn well and explained the Saxon/Roman style armor,elements,etc. The challenges of The Horror on the Hill were just as lethal and dangerous. Other adventure elements I just winged and it worked out great. Here's what I learned from that experience, Horror on the Hill is flexible enough to be mutilated into a retroclone system with little issue. I've heard of other friends of mine working with Swords and Wizardry and other basic clones to get the most adventure utility out of B5. For me the dragon's presence & corruption spread itself throughout the region causing all kinds of havoc in the area for the ten or so years it was there. It mutated and caused havoc with the locals until only the descendants of the local regions remain. The Dragon is far more Lovecraftian, and yes I realize that there are no dragons in AS&SH but its a dimensional traveler and this was a one off event.
The weird fairy tale like nature of Horror on the Hill might be adapted into Lamentations of the Flame Princess as a part of a dark fantasy Europe in some back water and remote area such as Russia, or the upper parts of Hungry or another remote location. The pulpy morass would fit those areas very well.
To overcome to the 'Dwarf problem' of AS&SH, I've made the Dwarves of D&D mutated descendants & children of the maggot things of Hyperborea. This totally creeped out the players and made the Dwarf players quite happy. The sword & sorcery themes of Horror on the Hill lend itself to a variety of playing styles and for myself I turned the volume up to eleven resulting in a pretty damn good basic adventure experience for the players while giving them the lethality that they've come to expect in old school games.
Are there system differences and issues? Some but not as many as you might expect, some of the witch encounters had to be redone with nods towards AS&SH system. Magic items were reduced down to far more mundane treasures, and the encounters were pruned and made more Conansque. But surprisingly the adventure not only survived but the players had a blast.
Despite warts, a few wonky encounters, and some really weird choices in placement Horror on The Hill is an old favorite of mine that can be used with a wide variety of old school play styles. I think it still has a place at the table and with some adjustment remains a pretty good crossover point adventure from the classic TSR D&D output into Electrum age old school role playing.