@Obscene SymphonyNone of the engagements are permanent, tbh. This is how they are from the start- the arrangements before the gathering of royalty. During or post-gathering, it's quite likely that, given some good reasons and persistence, one can get their engagements changed. In Niklas's case, he might break the engagement between himself and Mai in favor of, say, him and Raven. It'd damage relations a little with the Empire, but it'd bring Aciras even closer- he'd just have to convince his father that it's a better idea for him to marry into the Aciras royalty (and vice versa) rather than the Empire's royalty (and vice versa).
...so it's up for debate, essentially.