These four characters from The Last Kingdom survive for longer in the show than their counterparts from the book series for various reasons.
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.
As The Last Kingdom television series has grown, the show has been forced to depart more and more from the source material. Storylines inevitably get left out to make room for others which causes a ripple effect in the story. When one storyline is left out, it leaves out the foundation for another story. The show has to either leave out that story or create a new way to tell it. This leads to deviations in character arcs, requiring some characters to be merged and others to be kept alive longer than they are in the novels. For these reasons, these four characters outlive their storylines from the books.
4 Father Pyrlig
According to the books, Father Pyrlig is the first character who does not live to the events depicted in Seven Kings Must Die. Nevertheless, Father Pyrlig is easily one of the most beloved characters on the show, which explains part of why he was kept around longer than he should have been. Father Pyrlig plays a fairly important role in Seven Kings Must Die, taking some significant injuries in the Battle of Brunanburh, along with Uhtred. It's unclear if he survives those injuries after the battle. However, according to the books, he should have been long dead by the Battle of Brunanburh.
Father Pyrlig dies peacefully off-page of old age in the book series. His death comes between the seventh and eighth books, The Pagan Lord and The Empty Throne. Pyrlig is the same lovable warrior-priest in the books, but he is less involved by far. However, Pyrlig became such a popular character in The Last Kingdom that he was kept around and given a new role in Seven Kings Must Die. He also plays a more prominent role in the show than in the books, even when involved in the same events or conflicts.
3 Stiorra
Stiorra, Uhtred's only daughter, is another character who outlived her time in The Last Kingdom, according to the books. While Stiorra does not appear in Seven Kings Must Die, she is still alive at this point in the story, living with the remnants of her and Sigtryggr's people. At the end of The Last Kingdom season 5, Stiorra kills Brida and takes her people into the woods of Northumbria. Stiorra is an important character in The Last Kingdom, and while it may come as a surprise that she did not appear in Seven Kings Must Die, it makes perfect sense, seeing as her character arc had reached a fitting end.
In the books, Stiorra is killed in the conflict that leads to Sigtryggr's death in The Last Kingdom, season 5. She is killed in the books by Skoll Grimmarsson, the uncle of Sigtryggr. Skoll attacks Eoferwic when Uhtred and Sigtryggyr are leagues to the south, trying to find Skoll's army. After Stiorra's death, Sigtryggr becomes a king in Northumbria, marking a drastic deviation from the storyline in The Last Kingdom season 5, in which Sigtryggyr is executed by Uhtred after his revolt against Edward is put down. Stiorra's death in the books is a heartbreaking moment and could have been one of the saddest in the show.
2 Aldhelm
Aldhelm is another character who should not be alive when the events in Seven Kings Must Die come around. In Seven Kings Must Die, Aldhelm is hanged by King Aethelstan because he warns Uhtred of Ingilmundr's plan to kidnap him in the middle of the night. Aldhelm is not only dead by this point in the books. He is almost an entirely different character. In the books, Aldhelm is a loyalist to Lord Aethelred of Mercia and tries to kill Lady Aethelflaed instead of saving her as he does in the show. He is later stabbed in the neck by Uhtred in book 5, The Burning Land.
As mentioned, Aldhelm is a much different character in the books. In the books, he is sent by Aethelred to seduce Lady Aethelflaed to create legitimate grounds for a divorce. Aldhelm's character in The Last Kingdom seems to be a mix of the Aldhelm, who advises and follows the orders of Aethelred, and a character called Merewalh. Merewalh is a loyalist to Aethelflaed and becomes a trusted advisor in Mercia. The show likely mixed these two characters together to save time and keep a well-liked actor in the cast. Aldhelm became popular with fans which may have contributed to his extra time on screen.
1 Young Uhtred/Oswald
Young Uhtred is another character that dies in the books before the story's conclusion. Young Uhtred, mostly known as Oswald in the books, does not appear in Seven Kings Must Die, but it is mentioned that he is alive and living in Rome. Uhtred and Young Uhtred are able to have a loving relationship in The Last Kingdom despite their differences. This is not the case in the books, however, as Uhtred mockingly calls his son Judas and strips the name of Uhtred from him because he is a bishop, not a warrior. After that, Young Uhtred chooses the name Oswald for himself.
Oswald is killed in the final book in the Saxon Stories series, War Lord. He dies in a raid conducted by Ingilmundr, presumably, the one that killed Ingrith and the others in Bebbanburg during Seven Kings Must Die. Besides this, Oswald's arc in the books is similar to Young Uhtred's in The Last Kingdom, including being castrated by Brida. Oswald also survives up to the events in Seven Kings Must Die, unlike the other characters on this list, but he does not make it through Inglimundr's raid, which happens in the movie.
