Spawn of Lillith touches on a very old and slightly disturbing mythology. The Doctor gives the PG-rated version of it when he tells Rose and Wyn about Lillith, the First Woman in the Jewish creation story. What is left out is a lot of post-watershed material. Lillith, according to the Talmud, objected to the “missionary position” in sexual relations with Adam and demanded the right to be dominant. And the whole succubus, incubus mythology is all about sex and sexual abuse. In history they have often been a cover for sexual abuse, rape, incest and worse. The story of Lillith, meanwhile, is FAR more complex than the simplified version in this story.

There have been other instances of the Succubi and incubi in fiction, of course. The horror genre is especially partial to them. And especially erotic horror. More down to Earth examples have appeared in Poltergeist: The Legacy, where, as in this story dead loved ones were used against the victims, and Buffy the Vampyre Slayer. In the Torchwood Episode, Day One, an alien who uses sexual intercourse to absorb Human lifeforce is a modern twist on the theme.

The piece of poetry quoted by The Doctor as part of the Gallifreyan marriage ceremony, is, in fact, a Bahá'í Prayer.

O Lord, my God and my Haven in my distress! My Shield and my Shelter in my woes! My Asylum and Refuge in time of need and in my loneliness my Companion! In my anguish my Solace, and in my solitude a loving Friend! The Remover of the pangs of my sorrows and the Pardoner of my sins!

Wholly unto Thee do I turn, fervently imploring Thee with all my heart, my mind and my tongue, to shield me from all that runs counter to Thy will in this, the cycle of Thy divine unity, and to cleanse me of all defilement that will hinder me from seeking, stainless and unsullied, the shade of the tree of Thy grace.

Have mercy, O Lord, on the feeble, make whole the sick, and quench the burning thirst.

Gladden the bosom wherein the fire of Thy love doth smolder, and set it aglow with the flame of Thy celestial love and spirit.

Robe the tabernacles of divine unity with the vesture of holiness, and set upon my head the crown of Thy favor.

Illumine my face with the radiance of the orb of Thy bounty, and graciously aid me in minstering at Thy holy threshold.

Make my heart overflow with love for Thy creatures and grant that I may become the sign of Thy mercy, the token of Thy grace, the promoter of concord among Thy loved ones, devoted unto Thee, uttering Thy commemoration and forgetful of self but ever mindful of what is Thine.

O God, my God! Stay not from me the gentle gales of Thy pardon and grace, and deprive me not of the wellsprings of Thine aid and favor.

'Neath the shade of Thy protecting wings let me nestle, and cast upon me the glance of Thine all-protecting eye.

Loose my tongue to laud Thy name amidst Thy people, that my voice may be raised in great assemblies and from my lips may stream the flood of Thy praise.
Thou art, in all truth, the Gracious, the Glorified, the Mighty, the Omnipotent.

http://www.bahaiprayers.org/assist7.htm

http://en.wikipedia.org/wiki/Incubus_%28demon%29

http://en.wikipedia.org/wiki/Succubus

http://en.wikipedia.org/wiki/Lilith