The Far Shores are a mysterious territory in the Underworld controlled by pythian entities called Shining Ones. To modern Stygians, the Far Shores are territories controlled by Heretics, and not to be trusted.
The truth is somewhat more complex. Ferrymen know that the purpose of the Underworld is to help those souls which have ended up there to leave through Transcendence; to that end, the Ferrymen have always supported those Wraiths willing to help others achieve that goal. The Shining Ones are such Wraiths, and the Far Shores are their spiritual healing centers dedicated to helping wraiths transcend.
However, in an underworld where every Shadow is looking for an opportunity to ruin that plan, more than one Shining One has fallen. There are many Far Shores run either by fallen Shining Ones, or by madmen who saw the fallen ones and thought they had a good thing going. The most notorious of these, the Paradise of the Fishers, is an early Christian vision of Heaven that strikes everyone else as a gateway to Hell.
For centuries, the Ferrymen have maintained relationships with the honest Shining Ones, helping them to maintain stability through the Ritual of Severance. However, when the Ferrymen were exiled from Stygia, the Hierarchy took over this duty, and not understanding (or caring) about the finer details, shipped souls to whichever Far Shores asked for them. Oblivion was very grateful.