An aspiring Castle Keeper will often have many floor-plans of places through which unsuspecting player characters will venture, generally taking the forms of underground complexes or even wilderness or urban areas, but many likely do not have much stock for the "other" locales such as bastions, keeps, temples, and castles. This tome will remedy that situation and provide the Castle Keeper the tools and templates to design such from nothing or, if desired, to modify an existing structure with new and unknown (which may be otherwise familiar) traits. To start, it helps to answer very basic questions, making the needed background choices which will further assist as fine details are determined. Those who have read the first work, SG1: Engineering Dungeons, will find the procedure similar – please note that the former is not needed to enjoy or use what is here. In many senses, a "castle" is but a dungeon in a different sense, so an understanding of them is helpful but not essential. It may, at first, seem unusual that much of this work is focused on chapels or temples, but in the real world, castle structures were often built into, or from pre-existing, religious institutions, these being the bases for architectural endeavors for most of pre-Industrial history.