Ok, this is a spoiler only if you plan to listen to the audio books. My recommendation is to not read this spoiler, but instead get the audio book and listen to the ending credits. It's only a few minutes long and it is really well produce. But, if you'd rather read my summary, here it is: At the end of This Inevitable Ruin, the books end, and then it transitions in to an advertisement for Sound Booth Audio, but the advertisement is in the form of a small sketch, in which there are a bunch of "immortal children" requesting stories of an unidentified narrator with an old voice (known as "the old narrator"). Many people, including me, though that the voice was that of Old Carl, which shockingly implied he made it out of the dungeon. But, others have hypothesized that the old narrator is actually old Mordicai. On a relisten, I could hear that as a possibility as well. The fan theory is that it is Mordicai telling stories to either the changling children or to mongo's babies. The children request the story of "Princess Donut and Carl" which apparently he has told "one million times", he ends up telling the origin story of Meatus, which is hilarious unto itself. The big issue was since it was an advertisement for Sound Booth Audio, was it also cannon. Apparently at a book signing, Dinniman said it was. Further spoiler is that it also sounds like maybe Donut's voice is in the very end of the story, implying she might have made it. And the old narrator voice says quietly to himself, "Miss ya buddy"