Dark Path

The Dark Path is a huge network of interconnected passageways residing in the Ethereal Void.

History
It was constructed by the Hierophants under guidance from the three Serpents to facilitate swift, convenient travel between the various Shrines and temples on Serpent Isle. In conjunction with a Serpent Jawbone, it is possible to use one of many Serpent Gates to teleport to the hub of these passageways. Each tooth in the jawbone enables admission to a particular Serpent Gate on the Dark Path, which in turn leads back to its corresponding location on Serpent Isle itself.

The Avatar exploited the Dark Path's network in Ultima VII Part Two as a means to travel unhindered around Serpent Isle.

How it Works
The Dark Path is an excellent way to travel fast on the Serpent Isle; however, a Serpent Jawbone is needed to enter it. Also, the fitting teeth are needed to open the doors inside the path, which block the way to the exit gates. The Serpent Jawbone (originally in Erstam's possession, and later obtained by the Avatar) enables teleport by just using a Serpent Gate. However, the teeth have to be found for the doors inside the path, and then placed into the jawbone. The teeth are small and difficult to find. Here is a list of where to find them:

Map
The paths are not marked in any way, so here is a map of the Dark Path and where the various gates lead to.