The Arcane Sanctuary can be entered through a portal found on the lowest level of the Palace Cellar. This portal leads to the centre of the Sanctuary, where the waypoint is also found.
From this point, there are four possible paths to take, at the end of which lies The Summoner and Horazon's Journal. Within the journal is the symbol of the True Tomb of Tal Rasha; displayed nearby are the six symbols of the six False Tombs. After the Summoner is defeated and the journal read, a red portal leading to the Canyon of the Magi opens; this portal does not linger from game to game.