The 'place' Dragaerans go when they die. The paths lead, eventually, to the Halls of Judgment. If you are 'lucky'. It consists of a seemingly incoherent series of trials and tribulations all intended to either prove your worth to the Gods or condemn you to wandering around for the rest of eternity in a veritable oblivion. If you manage to make it through the paths, you must still await your fate at the hands of the Lords of Judgment.
Each House has their own tradition and route to follow in the path, and a Dragaeran is expected to know by memory the correct choices or actions.
Currently it is believed that only 3 'people' have ever visited the Paths of the Dead alive and been able to leave in the same state: Vlad Taltos, Morrolan, and Zerika the Fourth. Aliera was allowed to leave alive, but wasn't all that alive when she entered. Although if Aliera truly conceives Devera in the future in the Paths, things may get tricky.
While the Paths of the Dead themselves are not actually in the same plane of existence as the Dragaeran Empire, they can nonetheless be reached by physically traveling to the far northeast of the Empire, across the Forever Plains, to Greymist Valley between Hanging Mountain and Gyffer's Peak, and following Blood River that flows through the Greymist Valley until one reaches Deathgate Falls, and then going over the Falls in some manner. At the bottom of the Falls begins the Paths of the Dead.