- “Here we are. 'Storm unleashed. The balance will falter until the vampire with a soul drinks from the Cup of Perpetual Torment.'”
- ―Rutherford Sirk[src]
According to Rutherford Sirk, the Cup was supposedly a mystical chalice that would solve the disruption in the fabric of reality caused by the simultaneous existence of two ensouled vampires. He told Spike and Angel that the one who managed to drink from the cup would be determined to be the subject of the Shanshu Prophecy.
After a long fight, Spike beat out Angel for the cup, only to find that it held Mountain Dew soda. In reality, the Cup was a hoax set up by Sirk under orders of Eve and Lindsey McDonald as part of their plot to destroy Angel and take control of the remaining vampire with a soul, Spike.