Frieren: Beyond Journey's End, Vol. 10 (manga)

Years before the end of the war against the Demon King, Macht, the most powerful of the Seven Sages of Destruction, made a deal with the lord of the fortress city of Weise in an attempt to understand human emotions. Although the deal was at first beneficial to both sides, Macht eventually transformed the entire city and all of its residents into gold. Now, the strange tale of Macht, the fate of Weise, and Denken’s own past will all lead Frieren and her companions to one of their most difficult confrontations yet.