Valdemar is a country founded by Baron Valdemar, who fled from the tyranny of the Eastern Empire with his people. What makes Valdemar unique from the countries around it are its Heralds. Heralds are Chosen by the Companions, spirits in the form of beautiful white horses. Heralds dispense justice, protect Valdemar's people, and generally keep the country safe. They are sometimes called "arrows of the Queen". It is required by law that the Monarch must also be a Herald. There is no such thing as a bad or evil Herald. The Companions, being spirits, have pretty high standards. But neither are perfect.
Heralds also have at least one gift of Mind-Magic. These
gifts are -
Surrounding Valdemar are Karse, Rethwellan, Hardorn, and Iftel. For centuries, Karse and Valdemar were at war, but are now allies (I'm not telling why, you'll have to read the book!). In these lands are the Dhorisha Plains, to the South, and the Pelagir Forest, the uncleansed lands, to the West. In the Plains live the solitary Shin'a'in and their famous horses. They guard powerful magical devices left over from the Mage Storms. In the Pelagirs live their cousins, the Tayledras. It is their job to restore the magic-warped Pelagirs to normal. Only rarely do the Shin'a'in leave their Plains, or the Tayledras their Vales.
You can read more about this in a series of books by Mercedes Lackey, divided into trilogies or duologies. Check the list of books here. Well, what are you waiting for? :) Kera