IIRC the Empire is interested in the power of the demon king, which is what Liznette's recently concluded arc was all about.
On the other hand, it's funny how the girls discuss this cloak-and-dagger-y conspiracy about someone distributing artifacts on the side of Kingdom without realizing that very guy is the one in their party. Even the narration pointed this out (but it's talking from one of the girls' perspectives on p. 7... which one of them?)
Anywa, let's move on to the Kraken fight, you don't talk about Krakens in a manga without actually having it show up...