Dark Chasm of Old question

I know that to face The Darklurker, I need to clear all three dungeons and light the torches within them. But are all of the dungeons accessible from the same location?

So far, I’ve found an entrance under Drangleic Castle and another in the Shaded Woods (though I’m not sure where the third one is).

Do I need to enter each dungeon through its respective entrance and complete them separately, or is there a way to access and complete everything from a single location?