After receiving Gwyneira's warning the king who looked like a child that had just been scolded by his mother and apologized to her before pulling out a sheet of paper and handing it over to Marcus.
"Here, these are the terms that we came up with to break off Mrazivý's engagement. And I just want you to know that earlier I just wanted to see how far you would be willing to go for my daughter and see how strong you are."
As much as the king had been acting obstinate and unreasonable, he really was just trying to test Marcus. He wanted to make sure that he was committed to Mrazivý and that he was not a pushover but could also be reasonable.
At the end of the day, he actually really did care for his daughter and wanted her to be safe, which was one of the reasons he wanted to force her out of adventuring and to settle down.
Of course, he also had his position as a king to think about and using marriage as a tool for political gain was quite common.