I had a Skype session with a lovely book club in Georgia this evening when the question of the character Stolas came up. Had we met Stolas earlier in the trilogy, they asked. It seemed he was such an important character that it was odd that he only showed up in the last part of The Descent.
Without giving too much away to anyone who has not yet read The Descent, I thought I would tell you a little bit about where the idea for him came from. Stolas is one of the hundreds of named demons from Hell. He was not a minor one, described in Johann Weir's grimoire Pseudomonarchia daemonum as "a high prince of Hell commanding 26 legions" of demons. He is also learned, knowledgeable about astronomy, botany and the like. Which seemed to make him suitable to be a servant of Adair. Of course, he is not an owl but as I wrote his part I pictured him as having an owl-like appearance and you can feel free to do so, too.