So I put up some reviews of the two Bloodstone modules I had back in the day and loved and at least saw some useful bits in (H1 and H2, respectively). That series continued in H3, another Battlesystem-centric adventure, and ended with H4.
H4 was notorious because it was for - ahem - level 18-100.
Yeah, 100th level characters.
When I was finally able to read a copy, the first thing I did was flip to those 100th level characters.
Let me spoil it for you now:
The 100th level characters are a gimmick.
These 100th level characters are demi-gods, basically. Circe the sorceress, Perseus, Hermes.
It's not even a well-done gimmick. Want to know how many spells the 100th level wizard has? Same as a 29th level wizard. The THAC0 of a 100th level fight? It's 4, just like at 17th level. Nothing except HP changes.
One of them is Hermes, a Deep Gnome Thief/Illusionist - level 100/7. Another, Perseus, is a 100th level Fighter/Paladin. In practice, this seems to be a 100th level Paladin, since he has all of the Paladin and Cavalier abilities, but also has "double proficiency" in a weapon - er, Specialization? I'm not sure. "Double proficiency" isn't otherwise defined.
The stats of the characters are extremely high - most of them have a 25, scores below 18 are not common unless they're basically dump stats (the Persus's Intelligence is only 17, for example, and Circe is only Strength 15) with no real effect on that character.
It could be fun to run heroes, but honestly, it's purely a gimmick. I can't tell if I'm more disappointed that they are 100th level-in-name-only, or relieved that they are.
Overall, 18-100 comes off as nothing more than an excuse to say the module can handle 100th level character and have heroes with more HP than the top god of pantheons in the deities book. So 100th level clearly means "excuse to have lots of HP and high stats."
The module says,
"We don't really believe that anyone has ever "earned" a 100th-level character, in the sense that the character was started at level 1 and worked his or her way up in a normal (non-Monty Haul) campaign. On the other hand, there's always the temptation to play, just once, a character of ultimate power."
Semi-ultimate, anyway - for all practical effect they're just the maximum level listed on the spell lists in the PHB or to-hit charts in the DMG. They don't need to be 100th level, it may as well be 1000th level or 250,000th level for how much effect it has aside from getting more HP.
The adventure is one of those ones where power and combat just aren't going to do it - too many fights are beyond your ability to win (100 liches or 10,000 zombies for example) no matter what. You just have more leverage in the more winnable fights (10 type VI demons, which I guess aren't limited to six of them anymore.) It's a gift of an "ultimate" character in a situation where that "ultimate" nature doesn't really grant you much. Even the guidance for a 100th-level game is pretty much all don't be nice to them, and don't give them anything except normal magic items, strict adherence to the rules, and nothing beyond the top-ends of the charts.
100th in name and HP only, really.
Disappointing. A gimmick, and not a really good one at that.