Leave the Ravencrest's Legacy zone

[Votan]

There is a quest called An Unclear Path which leads to Ravencrest's Legacy, which lets you "relive the past" and puts you in a scenario as Illidan inside instanced Black Rook Hold. Now after activating the first two moon guard portals, you can sacrifice your moon guards for mana. After doing this a few times you gain your first ability called Stormrage. This ability lets you jump to a short distance away. However, there is no pathing requirements, meaning you can actually jump right out of the hold in a few jumps if you find a place to stand on after each jump. Once you unlock your 2nd portal, jump onto the small outcrop above the doorway next to the portal. Then, facing the wall in front of you as you stand over the doorway, jump onto the top of the rampart above you to your left. Now you should be standing on the top of the castle.

Once you jump over the main entrance, which is supposed to stay blocked, you can explore the small area around the hold however the area is small and it drops off, leaving only the void if you walk too far. It also makes you leave Illidan form, allowing you to mount up, etc as your normal character. I'm not sure any uses this may have but there may be some. You can even go fishing here, catching legion fish without the risk of people reporting you.

EDIT: if you want to get back in, you don't need to hearth or anything. Just walk right if you're facing away from the main entrance, and run through the first village, and walk up a path on the right until you turn into Illidan again. Then use Stormrage to get onto a tall tree or one of the ramparts, then leap into the small clearing and you will be "in" the castle area again