If you get this achievement, and subsequently get rid of the two necklaces, it will not count as completed in your Achievements window... which will stop you from completing the other Achievement: Tactician of Bloody Kithicor. It's not that much of a hassle to do again, but it is mildly annoying to figure out if you are trying to do all of the Hero's Journey.
You don't get the reward more than once though, even if you complete it again.