According to the books, these four The Last Kingdom characters should be dead by the time of Seven Kings Must Die. The Last Kingdom: Seven Kings Must Die wrapped up the franchise's story, covering parts of the last three of Bernard Cornwell's Saxons Stories on which the series is based. Seven Kings Must Die has received somewhat mixed reviews, but the response from fans has been generally positive. While perhaps not reaching the level of quality obtained in the early seasons of The Last Kingdom, Seven Kings Must Die did a decent job of wrapping up the show's biggest storylines and completing the most important character arcs.

https://screenrant.com/every-last-kingdom-character-dead-original-books-story-timeline/