Am I the only one bothered by the fact that Dagio's stats in no way take his immortality into effect? No fast healing, no regeneration, no special abilities with rejuvenate characteristics...nothing. In fact, he is just a dire rat with three character levels. We are left to assume that his immortality is merely a plot device that is completely irrelevant to the battle. My assumption is that the extent of his "immortality" is that he doesn't age, but can still be killed by violent means. Therefore, he is "ageless", not "immortal".
I decided to give him Regeneration 1/Magic. Magic created him and therefore magic must destroy him.