Sacrificial Lobby is located in Bloodfog Valley. You can't actually see the area from the world map as it's inside the area Altar of Sacrifice.
You can also reach the level 55 dungeon here by talking to the Guardian of the Relics.
- Apprentice Enchanter (There are two of them on the map)
- Guardian of the Relics (Dungeon)
- Manelov the Lava Collector