Ghost in the Veils by Jonathan Moeller
The tale continues. Spoilers ahead for the earlier Caina books.
It opens with her bringing along the corpse from the end of the last book and getting confirmation that it had never been human. And returning home to the dealing of problems with the children, since Kylon and Kalliope still are not getting along.
The Cult of Rhadamathar rears its head again with an attempted murder of the Great Royal Wife, while she is pregnant. Caina is asked to venture back to Istarinmul and find out why, and the attempted murderer. She brings Kalliope to help, as Kylon is better able to protect the children.
It involves her many associates in the city, Sophia professing respect for Morgant's great age, a badly planted piece of evidence, a mother who does not want her baby to inherit the throne, and more.