I am reading Hild and I have not been able to discover the definition of "haegtes." I read on my Kindle and cannot find the word on Wikipedia and have not been able to discover a reading group source; maybe I haven't looked hard enough but then I work full time.
I enjoyed your book Slow River.
[This email was edited for readability.]
A hægtes is a supernatural figure (imagine a witch, but worse).
The word is defined in the glossary—the list of terms and their definitions—that comes with the book. If on your Kindle (or in the Kindle app) you go to Table of Contents, you'll see the link to that glossary. It's at the end of the book, along with Author's Note which includes information on the real Hild and a pronunciation guide. At the front of the book, that is, before the chapters actually begin, you'll find other goodies, including a map and a family tree.
If you prefer to download and/or print the PDFs of map, glossary, pronunciation guide, list of characters etc. you can go to the Hild extras page on my blog where all are handily listed and linked.
This blog has moved. My blog now lives here: http://nicolagriffith.com/blog/