I didn’t find clear directions to this important area elsewhere, so I want to make it easier for others to follow the Hidden Path. This post relates specifically to the final entrance on Asterkarn Road. I missed this quest entirely my first play-through but was more thorough the second go-round. Others have adequately discussed where the quest begins and the earlier stages, so I won’t repeat that. I will mention that the quest begins in the Act I area but you need dynamite to gain admission which you can’t find before Act II, so if this is your first play-through, make careful note of any location in Act I that requires dynamite!
Asterkarn is a long, winding road trending northwest with several fortifications along the way. One of them has a unique profile which you can see in the picture I supplied. This structure is just north of the Asterkarn Road Rift. As you descend the stone steps, stay firmly to the LEFT. You will then perceive a narrow path off the map going east at the location on the picture where my marker appears. If you have obtained the necessary objects, the stone at the end will move to admit you to your destination.
Attachment: Hidden Path.jpg