Responses
He is likely turning Rubin's plan back against him. They specifically pointed out that Rubin is unmarried too, maybe he is setting up Rubin with the foreign princess and also like poisoning Alicia so she acts crazy.
Yup from what I understand
Wait what? What is he cooking? I thought it was like preliminary preparations for a sudden royal wedding of Kiel and Asha but then he mentioned Rubin...
I'm guessing that he's planning to stall time and weaken Alicia at the same time by marrying off the Duke into another empire mentioned chapters ago? And the potion mixed to his drink is a sleeping potion so the Duke will be clueless and helpless about everything?