During Prophecy from the Past quest, you will have to speak with pirate Hagar spirit (after you kill it in sunken ship instance).
He will ask you to talk with Norak and Fanatic. Those two will give you a side of a story, and you have to chose which one you'll tell to Spirit.
I chose Norak side of story and i got a book to upgrade normal lagmur to Guardian Lagmur, I think if you choose Fanatic story, you will get Deterrent Lagmur.