Legends of the Age of Sigmar: City of Secrets
City of Secrets is a novel by Nick Horth. It was published in 2017. It's set some decades after the The Realmgate Wars storyline and is published by Black Library in the Legends of the Age of Sigmar series.
Excelsis is the city of secrets, a grand and imposing bastion of civilisation in the savage Realm of Beasts. Within its winding streets and shadowy back alleys, merchants deal in raw prophecy mined from an ancient fragment of the World That Was, and even the poorest man may earn a glimpse of the future. Yet not all such prophecies can be trusted. When Corporal Armand Callis of the city guard stumbles upon a dark secret, he finds himself on the run from his former comrades, framed for a crime he did not commit. Only the Witch Hunter Hanniver Toll knows the truth of his innocence. Together the pair must race against time to save Excelsis from a cataclysm that would drown the city in madness and fear.
Despite being released in the Legends of the Age of Sigmar series, which contains only standalone novels and anthologies, City of Secrets started the story of Callis and Toll, two characters whose adventures continued in the Callis and Toll series.