The world of Red Tide is post-apocalyptic D&D. An unnatural disaster swept over the world 300 years ago, covering nearly everything in a red mist wherein followed demons and monsters. Survivors fled across the ocean and colonized a distant island archipelago; in the intervening centuries, the mists have covered the rest of the world, but are unable to encroach on the islands; many who now live on the islands are corrupted to worshipping the powerful demons (Tidespawn) that live just beyond the horizon in the waiting mists.
Sound interesting? Zonkers, there's a lot going on in this kind of campaign frame. You've got a Lovecraftian apocalypse, themes of survival horror out there in the mist, island hopping, and pulp action against cultists that worship the mist. Horrors emerging from a mist are an excellent theme - you've got great stories leading the way like John Carpenter's movie, The Fog (the original), or Stephen King's short novel, The Mist.
Let's take a look at some of the other opportunities here. First, diverse cultures: The ancient colonists came from various areas fleeing to the islands and settling the largest land masses, so you have cultures analogous to Imperial China next to Feudal Japan next to the Vikings and Celts and Teutons. Don’t you want to see a Viking Axeman fighting side by side with a Samurai and an Asian Wizard? Yeah, I love it, too.
The scope of the world is small - the encroaching red mists hang just beyond the reach of the islands, limiting the size of the initial campaign world to a manageable size. It creates the cultural diversity and intrigues of a massive setting in a bite-sized chunk. The smaller uninhabited islands are like dungeons (or planets, in a sci fi game) - each one is compartmentalized and can have a distinct theme; one island can have dinosaurs, the next can be overrun with cannibals, the next can have ancient ruins.
Higher level characters can actually enter the mist and survive the horrors they'll meet, wandering the post-apocalyptic ruins of the ancient cultures and battling the demons and demon lords that live out there. Planar adventures without leaving your home!
The premise for this campaign is pretty strong. But in addition to setting the scene, the sourcebook provides excellent support for creating a sandbox game - I posted some notes on it yesterday (Making the Sandbox, Red Tide style). In addition to the sandbox tables, there is cultural support in the forms of tables to generate names, tables for NPV motivations, room dressing, businesses, some map geomorphs - useful stuff for any campaign. I loved the tables on "quick cult creation". There are Red Tide specific new classes and spells (yawn...) - house rule crunch rarely does much for me - but if you're excited about that kind stuff, it includes a half-elf race-class caster, a humanoid witch class, and a few flavors of monk - fitting for some of the Asian-themed cultures.
On the other hand, the new monster section is both crunchy and excellent. There is an entire class of new creature called the Tidespawn - humans corrupted into mutants by the red mist - and a higher class of Dream Lords as major rulers within the red mist. The Dream Lords are equivalent to Demon Princes or Arch Devils in terms of power. The Tidespawn are horrific, insidious, the very stuff of nightmares - there are 7 samples listed, and this is an area where a creative DM could cut loose with their imagination to make all sorts of corrupted horrors.
The only part of the book I thought was a bit weak was the section on "Secrets" - it provides some explanations for why the red mist exists, why certain humanoids are immune to the corruption, that kind of stuff. The by-the-book answers didn't excite me. Thoughtfully, there's a big disclaimer about ignoring the chapter and coming up with your own explanations.
On the Beedometer, I rate this one 4.5 stars. Red Tide is proof that excellent campaign settings can be packaged like a dungeon master's tool box. The craft of presenting information to structure a setting is evolving; we may be using rules sets that date back 30 years or more, but the skill of today's publishers is improving. The bar is raising!
If you're a DM that runs a sandbox game, I would highly recommend checking this out to soak up the alternate techniques for generating locations and content; there's also good value in the other DM tools and tables, and plenty of nice monsters to borrow. Good job, Sine Nomine.