I know this question has been several times before, but no one has mentioned how to get over the giant wall in the middle of Triton Avenue. I've looked for stairs, but I can't find any. Do I have to complete a certain quest before I can get there?
If you look around, you'll find a portal (a big circle on the ground). If it's lit up (blue), you can use it. The portal connecting the two halves of Triton Avenue is available to all. Once you go through the portal, you'll be able to get to the Haunted Cave.
Other portals, such as one by Blad Raveneye, may not be lit up; to enable those, you need to do some quests.
If you turn your quest arrow on (CTRL+T), the arrow should guide you to the portal you need to use. This is useful, as other portals exist later in the game, and the quest arrow will help you find those.