It talks about the role of Witches in Castille, Aragon, and Navarra. They frequently act as messengers and neutral mediators between various lords, kings, merchants, and the like. Long ago, witches would fight with lords' armies, supporting them with flying scouting and powerful magic. Any witch who emerged would be recruited by some lord who already had the loyalty of a few other witches, and not have much choice about it. Witches cannot hold nobles' positions, so they couldn't marry the lords or knights as some wished to. They frequently were forced to fight other witches in petty wars. Then one day a great many of the witches serving evil lords against their will revolted, all at once. Most of the evil lords were killed, and the rest kicked out of power. Things were unstable for a while after that, but then two great kings formed the holdings of Castille and Aragon, and made a pact never to use magic in their wars.
Things are better for witches here now, which is good, because magic is a blessing from God. Here are some of the things Witches can do: Make pretty lights, make those lights stronger and explode-y, fly on brooms, make magical shields, and one "special talent" for each witch, such as healing wounds or bending wood like dough under their hands.
(In Navarra, witches mostly keep to themselves, though they band together into mighty magical armies if the region is threatened.)