Persephone

 was the wife of Hades, ruler of the Underworld.

Persephone saw good in Katarina and brought the First Doctor to the Underworld so he could help Katarina in her journey. When Hades' judges ruled that Katarina was neither good nor evil, Persephone convinced Hades that Katarina was good, and Hades allowed her to enter the Elysian Fields. (PROSE: Katarina in the Underworld)