There's one prominent character in Scylla and Charybdis who never utters a word ... of dialogue, that is. She has a full range of sounds and expression at her disposal.
I'm speaking of Penelope, who is a kearl: a genetically engineered monkey-cat hybrid, designed to be a comfort and companion animal. I came up with kearls in a backwards fashion. I had recently reread the Evil Overlord list: one hundred strategies (and then some) for surviving as a fictional villain. They range from "if I have a fatal weakness, I will fake another one," to, "If the princess refuses to marry me, I will say 'oh, well,' and kill her."
As mentioned elsewhere, I participated in an online writers' conference / workshop during the building phases of Scylla and Charybdis. Influenced by an item on the Evil Overlord list, I said that I wanted to have some kind of monkey-like companion animal, but it was *not* going to help the main character out of prison by stealing the keys from a guard. Beyond the joke of it, I liked the idea of my narrator being accompanied by a clever pet.
And so ... the kearl was invented. I wanted the creatures to be quick and agile, empathic and loyal to their people, but also quite independent. Penelope in particular is the companion of Anaea’s dear friend Orithia; how she ends up with Anaea is matter for the books. (Or rather, the book.) Penelope turned out to be a welcome addition to the story and a strategic source of comic relief. It's good to have an ally, even a furry one.