The Nature of the Night Mother.

The identity of the Night Mother has been one of the bigger questions in the elder scrolls lore. Some claim she was a member of the thieves guild who was kicked out of the guild for her methods, some say she is a former Morag Tong agent, some like myself believe that she is actually Mephala. The truth is much more complex than this however. All the in-game books about the Night Mother contradict each other and even history, it is to be expected that the Dark Brotherhood doesn't want their secrets known, if they even know them to begin with.

Sermon 22 speaks of the Night Mother:

>And then Vivec withdrew into the hidden places and found the darkest mothers of the Morag Tong, taking them all to wife and filling them with undusted loyalty that tasted of summer salt. They became as black queens, screaming live with a hundred murderous sons, a thousand murderous arms, and a hundred thousand murderous hands, one vast moving event of thrusting-kill-laughter in alleys, palaces, workshops, cities and secret halls. Their movements among the holdings of the Ra'athim were as rippled endings, heaving between times, with all fates leading to swallowed knives, murder as moaning, God's holy rape-erasure of wet death.

The “darkest mothers of the Morag Tong” are described as individuals who move as one entity. What if this explains all the contradictory Night Mother stories? What if all the stories are true, because the Night Mother is Mephala, who has been mantled by numerous people in the past?

Consider this, when a person performs the Black Sacrament they make an effigy of the intended victim and stab it multiple times with a blade rubbed with the petals of a Nightshade flower. But what if the effigy isn't of the victim? Remember the prayer uttered by the employer, "Sweet Mother, sweet Mother, send your child unto me, for the sins of the unworthy must be baptized in blood and fear." This prayer is said while stabbing the effigy as if it is offered to it. The effigy is not of the intended victim, but the Night Mother herself.

With this knowledge I contend that it is clear that people have mantled the Night Mother/Mephala in the past because we have seen someone mantle her in game, and that person is Astrid. Throughout the entire Dark Brotherhood quest line we see Astrid spin web after web of conspiracy and murder, culminating in the eventual raid on the Falkreath Sactuary. Astrid is the mother of this Sanctuary and it's inhabitants are her children, ultimately it is the actions of Astrid that ends up killing them, she murders her own children much like the Night Mother before her. She then performs the Black Sacrament on herself, to pray to the Night Mother for a contract. She even says it herself “That's why I did... this. Don't you see? I prayed to the Night Mother! I am the Black Sacrament”

She becomes the Black Sacrament, becoming the Night Mother, becoming Mephala. It fits with Mephala's cruel sense of irony, that Astrid who feared the Night Mother would embody her so much.