Akara will grant you this quest upon completion of the Sisters' Burial Grounds. Akara informs the player of a Horadrim sage named Deckard Cain, whom she believes will be able to advise the Rogues on their present situation. Cain can be found in the town of Tristram; however, the journey is too far on foot, so the only feasible way to travel to Tristram is via the magical portal opened within the circle of Cairn Stones located somewhere in the Stony Field.