A third-party sourcebook on derro for D&D 3rd Edition. This includes details on biology and culture, combat tactics, roleplaying tips, customization options (including feats for improving derro senses, unique equipment, prestige classes, and custom spells), adventure hooks, and a location for a derro-based adventure. The customization options are OK at best, with a few (such as the bonding whip and the custom spells) being particular disappointments.

The presentation of the derro in this book spins out of the description in the D&D 3E core rules... but rather than the more common emphasis on derro madness, they give them a culture focused on personal glory and power over others. The result feels like a hybrid of duergar and drow, but is somewhat less compelling than either. This makes the book hard to recommend for DMs planning to use the derro, unless they're very specifically looking for a non-standard take - the opposite problem from other books in the Slayer's Guide series, which tend to be too conservative. (Originally posted on Goodreads)