When you zone into the Sanctum of Fear you will find yourself in a large room followed with a spiral ramp leading upward. The ramp has static spawns on each corner, and every time you kill a static spawn a wave consisting of 3-4 mobs will descend the stairs. At the top of the ramp there will be another chamber with Overlord Um Nix in wait. As soon as you approach, the Overlord and his adds will aggro.
Once they have been dealt with, look up to see you are in a large chamber with an inverted pyramid in the middle. Move up a level and slay all the lizardmen. At the inner corner of every quarter section of this level there will be a small idol. Right-click it and select 'Sacrifice a clay golem heart'. Left-clicking the idols will not work. After sacrificing a clay golem heart, four elite Thulians will spawn. Kill them as they spawn and once all four statues have been activated, proceed to the upper platform and slay Fright.