Multiplayer Lobby is a more social, traditional multiplayer mode in which you can either create your own room, or join one created by someone else. There are a lot of different parameters to choose from when creating a room, or filtering for one to join: room mode, race type, region, tr...
however, need to reach the second section of the Overworld called the Nocean. This is done after completing the Emotion of the Ocean quest where Torgue blows up the ocean with a ton of magic missiles. Once this happens, make your way down to Wargtooth ...