Mudtooth is a Vendor in Ward 13 who sells concoctions. He also will tell you stories if you select dialogue options ->I had some questions -> Can you tell me a story.
The first time you talk to him keep listening to all of his stories until he eventually tells you he need's some time before telling you more stories. I went and progressed the main story and cleared some dungeons and returned to Ward 13.
Second time I talked to him half way through his stories he gave me a special ring. Continue to listen to all of his stories until he needs to take a break again. Go progress the main story and clear dungeons.
Third time I talked to him he didn't have any stories to tell and instead gave me an amulet and said he was out of stories which is when the achievement unlocked.