Pain was an Eternal, one of the Menti Celesti, the goddesses of Gallifrey. She represented and embodied pain.
Pain was the daughter of Ricky McIlveen (a powerful human psionic) and Jasmine Surprise (the daughter of Chris Cwej and Ishtar Hutchings). (PROSE: Happy Endings) She and her younger sisters, who included Death and Time, were the Menti Celesti. In addition to being biological individuals, they embodied aspects of the dreams and thoughts of the Time Lords, some of whom saw them as gods. (PROSE: Human Nature)
Pain appeared to Bernice Summerfield in a dream, telling her about a vulnerable nerve cluster on a Time Lord's shoulder. (PROSE: Set Piece)
Pain, along with Death and Time, attended Bernice Summerfield and Jason Kane's wedding in Cheldon Bonniface. (PROSE: Happy Endings) In a junkyard on Ha'olam, a salmon-coloured Abyssinian cat and two other strays attacked Sam Jones' cat, who was Life, for invading their territory. (PROSE: Seeing I)