The Lannister House is in poor condition at the beginning of Game of Thrones Season 8. Cersei holds the iron throne, but it cost him – his three children died for seeking power. Still, she had her twin brother Jaime at his side. Cersei used his love for Jaime and the protection of his family to justify his cruelest instincts, even though these instincts caused him a lot of grief. After Jaime and Cersei met Daenerys Targaryen and Tyrion, the Lannisters committed to help the war against the White Walkers. But once everyone left King's Landing, Cersei revealed that she was considering doubling all the others and letting them be exterminated by the White Walkers. Jaime was not happy that Cersei forced him to keep his promise, so at the end of the season he left the north alone, leaving his sister behind him.
Cersei had already threatened Jaime with betraying her, and it is well known that she hates her other brother, Tyrion. In the first of Season 8, we see how Cersei plans to treat Jaime and Tyrion – she sends Bronn to kill them both with a crossbow. Cersei likes to make a statement with his murders, though – so the weapon that Qyburn gave Bronn to use on the traitor Lannisters is important.