Reliquary of the Nephalem is an event that can be found in Passage to Corvus in Diablo III, in a dead end section of the ruins lower than the main passage. Two Nephalem ghosts ask the player to help them rid the city of a few Enraged Phantasms and Blood Golems which come in 2 small waves. A Resplendent Chest is awarded upon completion.
This event can be found in one of the "fake" Passage to Corvus.