For those who have never played the Council of Wyrms campaign setting, this allows players the opportunity to play the dragons as PCs, and have demihumans as vassals. There are also rules for playing half-dragons and even Dragonslayers (or Slayer Mages). The power levels are much higher, obviously, to account for the raw power and strength of the true masters of the world - the wyrms. The council setting is on the Blood Isles, where the Dragon Council keeps the peace (or tries to) between the various dragon clans. Aligned against the dragons are the humans (whose very existence is banned on the isles, after the Dragonslayer Wars), the giants (especially the Frost and Fire giants), and the plotting of the dragon clans themselves.
If you already have the Council of Wyrms boxed set, don't bother to pick up this book, as 95% of the information in it is just reprinted from the boxed set. After looking through it, I could only find one item that was an expansion (the Dragon Sage), and the inclusion of the Undead Dragon Slayer and Slayer Mage from an article in the DRAGON Magazine. The inclusion of these bits doesn't warrant spending $26.95 on this sourcebook (which is about the size of the Players Handbook).
If, however, you don't have the boxed set, and are interested in starting up, or running in, one of these campaign settings, this is an excellent sourcebook. Much of the information in it can be transferred to other campaign settings as well. (The chaos created by introducing a Dragon Priest or Dragon Mage in a different campaign can be amusing for the DM, and challenging for PCs).
