Updated 04-05-2016 01:18 AM
This achievement is unlocked by defeating 500 Lycanthropes (Werewolves or similar shape shifting creatures). You can find them throughout Neverwinter, especially in the Gray Wolf Den Dungeon. This achievement unlocked naturally without much effort as I was leveling up to 42. You can also check your status by bringing up the menu, tab over to Quests, access the journal menu, tab once more to achievements, and scroll down to Slayer.