Everything we know about 'Fourth Wing' book 4, from Rebecca Yarros' hints to new clues in 'Threshing Day'

Author Rebecca Yarros has a new release set in her Empyrean world, but it is not the long-awaited fourth novel. The new title, "Threshing Day," is a collection of short stories that offers additional material from the same universe.

The update matters because readers have been waiting for a follow-up since the third book, "Onyx Storm," which closed with an unresolved ending. That book was described as a record-setting adult seller, increasing demand for the next installment.

The first three volumes arrived in quick succession. "Fourth Wing" was published in April 2023, followed by "Iron Flame" in October 2023 and "Onyx Storm" in January 2025, all within less than two years.

Yarros has said the fourth book will follow a slower schedule. At a Philadelphia appearance on January 25, 2025, she declined to promise a publication date, explaining that she intended to complete a contemporary novel first. She then shared little about the series for the rest of 2025.

Activity resumed this year. She said on Instagram on February 8, 2026, that she had started planning the novel, then announced on March 19, 2026, that drafting had begun. She wrote that her contemporary manuscript was with her editor and she was returning to the Empyrean setting, adding "Let's ride," according to Yarros. No publication date has been announced.