Wait, why did he turn him into a dragon if not to have him killed by humans? I think it would be the perfect justice, not to mention it would be ironic for him to be killed by a dragon hunter/slayer.

Well your reasoning is half right, it could be very ironic that he is turned into a Dragon and then a dragon hunter kills him, however you must remember that Jörmungandr said that the punishment will not be death, it will be life; for some people there are worse things than death, and that is what Dagur thinks about this situation right now, Jörmungandr knows it, so he will not give him something that he is considering as a way to go out of this.

Now, to tell the truth the reason behind this is a lot more complex than that, but I can not talk about them because SPOILERS.

I hope that this respond somewhat to your question, thank you for sharing your thoughts.

Ah, I see. These pages are posted so far apart, I forget things.

I think I know who is this new character...
Interesting! :)

Well I am glad that you like it and I hope that you are enjoying in trying to guess who is he, for now I can only say that he will be very important later.