Red Tide is a setting created early in Kevin Crawford's career, and now lies abandoned. It's kind of a broken mess of brilliant gears, because while initially designed for Labyrinth Lord (B/X D&D), it never really fit that (see below) and also the latest creation in the line was a core game (Scarlet Heroes) which was also not overly compatible with what came before. First an overview:
Red Tide (2011): Extremely interesting and evocative setting. One of the best, perhaps the best, written for the OSR. Had a killer hook, bringing all the cool together on one island - Vikings, evil samurai, good samurai, Chinese kung-fu fighters, Arabian dervishes, African Seers, even novel ways to explain how Dwarves, Elves (/Half-Elves), and Halflings "work".
It was a brilliant eclectic mish-mash. It has a full section on Slavery and Gender Roles. This was 2011, so there was no woke shit. Things are practically explained. Some societies are matriarchal, some patriarchal, and to make it simple Xianese (the biggest human society) is meritocratic with a dash of traditional patriarchal values. This has the blueprint for GM support that was present from basically here on. It may have existed in SWN first, but this was the first representation of it in a fantasy setting. Some of the elements from this book were never translated over (styling items to cultures), while others are purely incompatible (scions & Shou witches), and still others were completely made obsolete (the Bestiary section is garbage if you have Scarlet Heroes).
One of the issues with this game is an understated E6 inherence (IE it expects PCs to be 6th level or less forever). The strongest enemies you run into are 11 HD. That's for an infernal demon. The majority are 7HD or less. When Scarlet Heroes came out and topped at 10th level, I was not surprised.
An Echo, Resounding (2012): Domain management and warfare system miles better than the bullshit dreamt up by Alexander Macris for ACKS at roughly the same time. AER is so good it's never been properly copied, expanded upon, or updated. It is a completely separate subsystem so is usable with basically any OSR. It is also flavored toward Red Tide so there is a minor limitation in that regard. Also heavily details The Westmark, a section on "the Borderlands" of Red Tide that's ripe for adventure and hexcrawling.
Looking through the stats for armies and the like in the domain play section further insinuates the game expects PCs to peter out around 6th level (of B/X stats).
The Crimson Pandect (2012): A few months later this book came out, basically detailing half a dozen alternate Magic-User classes and one alternate Elf class. The spells and therefore spell lists are not great, Crawford has come a long way since production of this book.
Scarlet Heroes (2014): The last word on the Red Tide setting, this book is part reiteration, part expansion, and part playtest for Crawford's solo endeavors that basically completed in Godbound (2016). That section of the game was boring and unnecessary, it has luckily been limited in Sine Nomine productions since then. The new additions to the Red Tide setting are welcome, mostly in the form of new spells and unique monsters.
Ratings: I would say Scarlet Heroes is #1, Red Tide is #2, Echo is #3 and Crimson Pandect is #4, and mostly it's still on the list because the various classes have some good lore about the world baked in to them. I would dearly love to see Kevin revisit this setting and upgrade/consolidate all this material into 1 book with an underlying system within it that is much more B/X based and much less experimental and lame power fantasy as Scarlet Heroes.
