Tomb of Horrors is this year's super-adventure, a 160 page hardcover by Ari Marmell and Scott Fitzgerald Gray, featuring the legendary Acererak a demilich of great power, ambition and madness.
Warning: There are some mild spoilers, so if you plan on playing this adventure, think twice before continuing.
Unlike last year's super-adventure, Revenge of the Giants, this Paragon-tier module is actually split into 4 chapters of varying level from late Heroic to early Epic. Where Revenge of the Giants was a continuous adventure, the format of Tomb of Horrors is more like four (or five) separate mini-adventures, split up by other adventures you might want to run.
This edition of Tomb of Horrors treats the earlier adventures, S1: Tomb of Horrors and the Return to the Tomb of Horrors as backstory. Instead of adventuring through the original Tomb of Horrors, the PCs will go through four (mostly) new tombs, each with their quirks and challenges.
I've been rather critical recently about WotC's adventures published since 4e was started. While most of the time the combat encounters were interesting, there was very rarely any exploration like there used to be, little roleplaying outside of combat, puzzles were practically non-existent and the pacing was off. If you weren't fighting something you probably weren't doing much at all.
Tomb of Horrors is completely different. It is in my opinion, the best 4e adventure that WotC has published. Though there still aren't a ton of roleplaying opportunities, there is one section of the adventure where there are some.
Previous adventures featured a rather linear sequence of encounters, mostly combat, with very little in the way of empty rooms or interesting features without creatures. There is definitely a sense of exploration in this Tomb of Horrors. There are different paths to take, different things to poke around, and not every encounter needs to be encountered in order to succeed in the adventure.
Given that it is called Tomb of Horrors, there are definitely puzzles to be solved, although admittedly not as many as I'd like. I suspect this is because puzzles are very party-specific. It's difficult to have puzzles have a significant meaning in an adventure if you don't know if the party playing it likes solving puzzles. That said, it wouldn't be difficult to add some puzzles on your own. Still, I'd love it if WotC would publish an adventure on D&D Insider at least for those of us who love puzzles.
Tomb of Horrors still features lots of encounters, and the authors did an amazing job making each one interesting. They have a higher level of sophistication than previously seen, in that not all combats need to result in the eradication of the opposition. Some combats have goals that need to be attained. Some combats are fairly easy, some are nearly impossible and require the PCs to succeed at their goal and get the heck out of Dodge.
One major difference between the original Tomb of Horrors and this version are the traps. They still apply a 4e philosophy, mixing traps with monsters and not having instantly lethal traps. This isn't to say that the traps aren't dangerous though. While there are no save-and-die (or worse, no-save and die) traps, there are traps that will kill outright, although it requires some failed saves.
Given the historical lethality of the original Tomb of Horrors, there are recommendations for upping the lethality of this adventure. This includes increasing the damage of the traps (a good idea IMO) and starting the adventure at 8th or 9th instead of 10th level. I don't care for the latter idea, as this mainly would just result in longer combats.
There are lots of skill challenges as well, and they are creatively integrated with combat as well as stand-alone. I still think the way that the skill challenges are written are rather kludgy, but I'm not sure there is a better way to write these things.
As far as the monsters seen in Tomb of Horrors, there definitely is an emphasis on undead, to the point that I highly recommended that someone in the party be able to inflict radiant damage. The challenge will definitely go up if there is no access to radiant damage powers. The emphasis on undead is highest in chapters 2 and 3, which is why I am glad for the opportunity to take a break between those chapters and have adventures involving abberations or giants for example.
One thing I was pleased to see is that the new monsters definitely are using the new damage expressions recently updated in the errata and Monster Manual 3. Unfortunately, when monsters from earlier Monster Manuals are used, the original damage outlay is still used (I'm looking at a specific pair of iconic monsters in Chapter 4 in particular). This is understandable, but unfortunate. However, the weaker damage is so obvious, especially later in the adventure, that it's a snap to slot in the new values.
There is a battlemap featuring three of the locations in the adventure. To be honest, I'm not entirely sure why they chose these particular areas (with one exception), but the big map is generic enough that it could easily see re-use at some point.
Finally, those running this adventure in the Forgotten Realms shouldn't have too much problem at all adapting the adventure. Those of us running it in Eberron though, will have a bit more work to do. I find that any high Paragon or Epic adventure published by WotC so far is really tough to use in Eberron without substantial changes, due to the reliance on the 4e D&D World dieties and cosmology. The authors do have some suggestions in a sidebar, but I find the suggestions for Eberron a bit lackluster given some of the great villains and history that Eberron has available.
The bottom line is that if you've been unhappy with the adventures that WotC has published in the past, they're starting to listen to the criticism. Tomb of Horrors is certainly a quality product.