"Find Red Eagles Sword" quest is bugged.
Reading the book "The Legend of Red Eagle" triggers the quest.
However, if you complete the quest and then pick up another copy of the book, the quest will be re-added to your quest log.
I haven't attempted to re-complete it yet, but presumably this will be impossible - unless reading the book respawned all the mobs & items.
It might be linked to reading a particular copy of "The Legend of Red Eagle"
If so, the copy I read that caused the above behaviour was the copy on the dead bandit in the room immediately before your kill Red Eagle. (the room that contains the alter upon which your place Red Eagle's bane)
After googling, this seems a common bug:
For those of you who have completed this quest, have you had the quest pop-up again, when you read a different "Legend of Red Eagle" book? I just finished the quest earlier, but I was exploring a town and found "The Legend of Red Eagle" book again, and read it, and after I opened it, I got the quest added again, with the objective "Find Red Eagle's Sword" showing up in Miscellaneous Quests again, and showing a waypoint on the map.
I just had the same thing happen to me! I might go check it out tomorrow
I had it pop up again for me as well
I actually found the book again inside a tent right after finishing the quest. I then walked over to the corpse of the guy who had the Red Eagle's sword in the first place and sure enough the sword had respawned right back in his dead corpse. So yeah, it seems like you can get the sword multiple times.
Now I didn't go back to see if I could fight Red Eagle again and get another Greatsword, but I'm guessing you can.