The Chapel of Vanity, also known as the Cathedral of Light or Cathedral of Vanity, is a small uberlevel accessible from the Cathedral in Act 1. It only consists of a single big room where the boss Inarius and his minions all reside, protected by the Crystal Ball which exudes an invulnerability shield and must be destroyed first.
"How much suffering, mortal, does it take before you lose your grace? Let me show you..."
According to religious myth, the mortal plane Sanctuary was created by the fallen angel Inarius and the demon Lilith to serve as a refuge from the Eternal War. The two created a race of servants from the earth which were to worship them for all eternity. However, humanity broke free from its shackles when a small group of farmers rediscovered their birthright and ancient powers inherited from their supernatural parents. As the edyrem army grew, Inarius descended into megalomanic madness and was eventually destroyed along with his golden cathedral of vanity. It is whispered that the ghosts of Inarius and his closest worshippers still roam the cathedral.
The Chapel of Vanity is the last remnant of Inarius on the mortal plane, nothing more but a shell of its former glory.