The Queen of the Underworld is the title held by the consort of the Source of All Evil.
The demon Hecate was the first evil being referred to as Queen of the Underworld, though it is unknown how she attained the title. She sought to conceive an heir with a mortal, but was banished through the Jeweled Poignard of the Order of the Stephanine Cross.
Phoebe Halliwell is the second known Queen of the Underworld, having attained the title when she underwent the coronation ceremony with her husband Cole Turner, who had become the new Source of All Evil after being possessed by the essence. However, her reign was short-lived as the good inside her prevailed and she reunited with her sisters to vanquish Cole.
A Possessor Demon sought to become Queen of the Underworld by using Wyatt Halliwell to resurrect the half-faced Source and rule at his side. However, her desires were quickly shattered when she was vanquished by Piper Halliwell. As she was magically connected to the Source, he was vanquished as well.