Quest: The Tale of Captain Brage
You can find Captain Brage wandering around east of the center of the "Archaeological Site" (Area South of Lighthouse)
He will speak to you automatically and ask a riddle...answer anything but "Death" and he will attack you.
If you entered the area from the West it is possible to start the fight without proc-ing another character.
Killing him will give you the achievement, you do not need to complete the quest.
Note: The companion to this achievement will be lost on your playthough unless a save is reloaded.