At last, Codex Mysterium has been added to the database so I can add my review (it's only been a few months since I asked...I don't get it, I send in all the information asked for, but the products I ask to get added never seem to. I've got a handful just sitting on my hard drive waiting to be added. Oh well.)
Codex Mysterium is a sourcebook devoted to the Sovereign Stone magic system. It's a 200 page hard cover, priced at $30. So it's definitely a bit on the expensive side, though not hugely so. While meant for the Sovereign Stone campaign setting, the book can also stand alone as it's own d20 magic system. Unfortunately, you'd be missing a lot of useful spells if you don't have the Sovereign Stone campaign book.
Physically, it's pretty much exactly like the Sov. Stone campaign book. Fairly sturdy, thick and rough paper, average sized margins and type size. There's a lot of art, but most is not particularly spectacular and most are fairly small (and are in the center of the page).
The first chapter describes the various spell casting classes. It features the 2 basic classes (elemental mage and void mage), and has several prestige classes. It also describes several new feats, and adapts regular d20 magic feats to the new Sovereign Stone system. Some of this is from the campaign book, but most is new (and some is borrowed and adapted from S&S's Relics & Rituals).
Most of the prestige classes can be adapted fairly easily for use with regular D&D, because of how they were designed (magic ability increases by effective levels, like regular ones). The only difficulty is adapting the requirements, because most have a base spell casting bonus as a requirement.
One prestige class, the War Mage, is vastly overpowered. It has the best attack bonus progression, has two great saving throw bonus progressions, has a ton of special abilities, and gets to increase in spellcasting ability at the same rate as regular mages/spellcasters. They do only get 2 skill points, but even so, they're very very tough in practice. I just use them for NPCs.
Chapter 2 is basically from the Sov. Stone campaign book. It describes just how their magic system works. Basically, it's pretty simple. Each spell has a casting total, or CT. This is a number from 1 to 300 or so. Each turn that spell caster casts a spell, he rolls a d20, then adds a spell casting bonus. If that number if greater or equal to the CT of a spell, the spell is cast. If not, the player continues to cast it the next round, again rolling and adding the number to the running total.
The tricky part is, each round after the first the mage is casting a spell, he has to make a fortitude save, or suffer subdual damage. So the net effect, is that high level mages can cast simple spells all they want, but complex ones can take a long time and effort to cast, and are beyond the ability of low level mages.
In practice, I've found that it works pretty well - the system is a lot more flexible, but requires a lot more dice rolling and accounting. Some might not like it because of this, but as a fan of the D6 system from West End Games, I find number adding to be no big deal.
Chapter 3 desribes how magic fits into the Sov. Stone world. If you're not using the setting, this isn't too useful, but it's only 10 pages.
Chapter 4 is actually quite similar, only it describes the practical effect of the magic system on the Sov. Stone world. It goes into Mages Guilds, Temples, Alchemists, buying and selling stuff. While mostly useful for Sov. Stone games, it has some applications to other settings. This is fairly big at 25 pages.
Chapter 5 consists of new magic spells, and is the largest chapter of the book, at 60 or so pages. The spells are delightfully named (I think, anyway), and range from the very useful to the very strange. The upper power level isn't very high. For instance, Summon Lighting, one of the more powerful combat spells (it has a CT of 155) does only 5d12 damage to a target. The most powerful, Exploding Sun (CT of 248) does 12d8 damage.
As I said, many of the spells are downright weird. For instance, "Aurora", which lets the caster basically create a miniature Northern Lights, or "Sunburn", which gives the target a bad case of sunburn, or "Weather Beaten" which weathers an object (so it looks older). There are also a lot of practical spell, like ones for identifying plants, helping crops, burying the dead.
As mentioned, it does not repeat the spells from the setting book, and as a lot of those were very practical for adventurers, this hurts it's usefulness as a stand alone book.
Chapter 6 is on designing new spells. It's a very crunchy system - basically you figure out what you want the spell to do, then go through something of a check list which will give you a CT for it. Apparently it was originally designed by semi-legendary game designer Greg Porter, then altered for d20. I think it works pretty well, but like all forumla based things, can be abused.
Chapter 7 is on magic items. Basically it just has a few exmamples of magic items, and describes how they fit into the Sov. Stone setting. Like the spells, some of these are a bit quirky. For instance, "The Boots of Irwen", made from alligator skin, give the wearer a +2 armor bonus, but turn his skin green.
The eighth and last chapter is on making magical items. This is actually pretty simliar to the regular d20 method, only adapted for the Sov. Stone magic system. But you still have the similar magic item creation feats (ie, Brew Potion, Forge Ring, Craft Staff, etc)
Lastly, you get a complete spell list, of spells from all Sov. Stone products (up to the release of the Codex, which was the third product).
I think this is a very solid book. It's probably a bit on the pricey side, but it really has a lot of info in it. It's a definite buy for those who use the Sovereign Stone system. Really, just how valuable this book is depends on if you like the magic system or not. If you don't like the Sov. Stone system, you're going to hate this book. If you do like it, you should like this book a lot (though not the price).
Since I like the system, I like this book. But it's not perfect - most notably the one vastly overpowered prestige class, and also the price, which is a lot for someone like me who is broke. I also would have liked more magic items.
And it doesn't have enough artwork of scantily clad ork women, like the campaign book. I want more ork babes!
