I remember the original teases for this book, back when it was originally going to be called "Scroll of the Lesser Races." Wow, am I glad they didn't go with that title. Beyond the obvious implications, Exalted 2e has enough problems with overtones that only a few hundred people are important to the setting and how important they are can be determined by what color they glow if someone jumps them in an alley.
Scroll of the Fallen Races is divided into two parts, one for the Mountain Folk and one for the Dragon Kings. Both of these sections pretty much just recapitulate the information in first edition products--Exalted: The Fair Folk and The Exalted Players Guide, respectively--but update the mechanics for second edition and expand a bit on the things we already knew in the way that most of the second edition books do. For the Mountain Folk, this mostly involves making their society even more cutthroat and backstabbing and giving even more of the credit to Autochthon for inventing everything everywhere ever. Life for the Artisans is a seething pit of vipers with constantly shifting alliances and power plays and life for the Workers and Warriors is a nightmare dystopia, but it's "okay" because they're nearly living machines anyway, so who cares what happens to them? The Artisans certainly don't.
The rule of stupid distances is still is effect--Lutar, a Mountain Folk city-state between Mount Metagalpa and Great Forks, is described as conducting trade with and sending troops to help the Haltans, thousands of miles away--but for intra-Mountain Folk relations it actually makes sense because they have functional long-distance communications and travel technologies. The Mountain Folk are probably the only civilization in Creation where this kind of scale makes sense, and I wish that I could think it was planned instead of just being a consequence of not wanting to fill in the empty places in the map.
Most of the section is devoted to artifacts, character creation, and Charms after the first twenty pages, and while the artifacts include plenty of obvious modern technology with the serial numbers filed off like magical grenades, that doesn't bother me here. The Mountain Folk were put in as Exalted's version of dwarves--explicitly, see The Making of Exalted--so having them be superlative-but-mechanistic crafters fits in just fine. My problem with Wonders of the Lost Age is that it tried to make this everyone's paradigm, to the overall detriment of the setting, not with anyone at all using magitech. And if anyone's going to use it, dwarves are a good candidate.
The Charms are mostly utilitarian, as befits the somewhat focused nature of the Mountain Folk, though the Charms that replicate some aspects of sorcery (summoning elementals and countermagic) are conceptually the most interesting. Otherwise Worker Charms are boring, Warrior Charms are great for killing people but literally nothing else, and Artisan Charms are mostly manipulating Essence with a side order of crafting. Only the Enlightened Charms really have anything beyond a somewhat narrow focus, because that's where all the social and interaction stuff goes. Fortunately, these are accessible to everyone, since in a Mountain Folk game the PCs are all likely to be Enlightened. I doubt many people want to play "Boring 9-5 manual labor: the RPG."
There is one huge oversight I have to mention. For all the talk about the Endless War and how the struggle against hostile underground monsters and civilizations defines Mountain Folk civilization, the book doesn't give you any stats for anything to fight. That's a pretty big oversight and one that makes it hard to run any kind of Mountain Folk game involving their greatest threat without a lot of work on the storyteller's part.
While I'm a fan of the first edition corebook's explanation that the Mountain Folk are just Fair Folk who entered Creation at the Elemental Pole of Earth and took on some of its stability thereby, that ship has long since sailed. What's here is a serviceable if boring portrayal, but there's not much that actually makes me want to play a Mountain Folk or run a Mountain Folk game.
The Dragon King section is better, and is helped by spending slightly more time on Dragon King culture and psychology and by greatly expanding the scope of Dragon King locations. Originally they were all in Rathess until the Exalted Players Guide added the Pterok, Mosok, and Anklok breeds, but even there it was implied that Rathess had almost all the surviving Dragon Kings and the other three breeds were mostly afterthoughts. Scroll of the Fallen Races expands on these locations, like Mouth Eledath in the southwest, where the Dragon Kings have advanced far enough to begin trade with the Mountain Folk (in 1e they had just attained sapience within the last decade), or Scale Crest Island, where intelligent Mosok rule over human barbarian tribes on the coast and intelligent Anklok do the same from the island's interior. This is great and it's an important addition to the game, since it provides plenty of possibility to interact with Dragon Kings as more than monstrous manual entries.
As with the Mountain Folk section, most of the chapter is taken up with superpowers, but unlike the Mountain Folk the Dragon Kings don't derive their powers from Charms. They get them from stratified progressions of techniques called the Ten Paths of Prehuman Mastery. Each Path is themed to an element and has some particular focus; for example, the Clear Air Path is about perception and the Flickering Fire Path is about speed and motion. Unique to the 2e presentation of the Dragon Kings, there are also five Dark Paths themed around the five elements of the Underworld.
This is also a holdover from first edition, but I like it because it reveals that Charms are not the universal way to organize supernatural powers. It makes me wonder if the other Primordial-created races like the alaun or the scathach had their own non-Charm-based powersets and how they were organized. This is somewhat tarnished by the Fair Folk using Charms even through they come from the madness outside Creation, but it still makes me curious.
The storyteller advice correctly points out that the Dragon Kings have very similar themes to Solars--devotees of the Unconquered Sun who have been gone from the world for ages and who most of Creation thinks are monsters, who are driven by ancient memories--but points out that Dragon Kings have a much harder time proving their good intentions than Solars because they do look like monsters and there's no way around that other than disguising themselves. Dragon Kings have to contend with a world that they once ruled that has now grown strange and nearly forgotten them, when it doesn't remember them as horrible monsters. Okay, maybe it's closer than "very similar." But the Dragon Kings have no chance of ever regaining their power due to diminished numbers, so games about them are focused more on what they can do with their diminished capabilities in the Age of Sorrows.
Overall, the second section is much more interesting than the first, because even though the Dragon Kings are thematically similar to the Solars, they have enough breadth of concept and location that there are many more stories to tell about them than about the Mountain Folk. Plus, dwarves are cool, but they're just not as cool as magic dinosaur people. The prize goes to the second half of the book, but I still like the whole thing for showing two of Creation's nonhuman cultures in (some) depth. I only wish there were more interesting nonhuman races to show.