|The following is based on Van Buren and has not been confirmed by canon sources.|
Though some people think she is insane, the genetic knowledge she turned into a religion is actually helping the wasteland. She lives in the American Southwest, in a place called Ouroboros. The Daughters of Hecate are her prime servants, spreading Hecate's will to all the tribes. The Vipers, raider exiles from the West, have become Hecate's fanatical army, and will crush anyone who challenges her. The other tribes fear Hecate's power, and rightly so.
The Twisted Hairs tribe was one of the most domineering tribes in the wasteland. They regularly raided their neighbors for food, supplies, and slaves. They were merciless in their efforts and the other tribes began to fear even the mention of their name.
It was during the reign of the Twisted Hairs that Caesar's Legion rose to power. The Legion taught the tribes to fight back, and the Twisted Hairs were soon driven from their lands. Weakened and on the retreat, the Twisted Hairs were then set upon by the Legion and destroyed. No one was spared, although one woman did manage to escape. She later became the supposed goddess known today.
She wandered the desert passing from tribe to tribe trying to find someone who would take her in and give her a home. The tribes spurned her and turned her away. They told her that she was cursed, that the Legion had marked her, and that she would bring death to any who provided her help. Consumed with anger and hatred she fled back into the desert from which she came.
On her own, she was driven insane by the sun and sands of the wasteland. Embittered as well, she eventually collapsed from exhaustion. Fortunately, she collapsed near the Nursery; a worker robot sent out by Diana of the Nursery revived her and gave her the name Hecate. It was Diana that taught Hecate much of her genetic knowledge, Diana not knowing Hecate's state of mind and her consequent desire to use such genetic knowledge for less than noble purposes, much less her honest belief in both her own divinity and Diana's.
Diana eventually had Hecate leave, and Hecate returned, refashioned with warpaint and braids, to the tribes. There she instituted a religiously-cloaked system of eugenics, slowly taking the strong sons and daughters to become warriors for the Hounds of Hecate, leaving only the weak and infirm. Hecate's eventual plan would be to take these Hounds of Hecate to sweep down on the tribes as well as Caesar's Legion in violent retribution.
Background on Hecate's name
"I see that you are awake at last," it said with a woman's voice. "I am Diana. Can you tell me your name?"
"I... I don't..." She paused as she tried to remember who she was, struggling with the blackness that was her mind. "Dark Mother," she blurted at last. "They called me the Dark Mother."
"Did they, now? Well, I shall call you Hecate then. Do you mind?"
"Yes. Forgive me, I know you don't understand, but I find it amusing. You see, I am Diana, and she was the goddess of the full, or bright moon. Hecate was her opposite, the goddess of the new, or dark moon. She was also known as the Dark Mother. So, I thought I would christen you Hecate."
"Yes. Both were goddesses of the moon... Forgive me; I must be confusing you to no end. I've been alone for centuries and I find myself babbling now that I have someone to talk to. Come. Let me show you my world and we will talk and get to know one another. There is much that we can learn from each other."
Interactions with the player character
The player could take her down and free the people from her tyranny (and possibly weaken them in the long run) or let her religion prosper (and build a hardier stock of people that could better survive the rigors of the wasteland).
Hecate has not appeared nor is she mentioned in any published game. She was to appear only in Van Buren, the canceled Fallout 3 by Black Isle Studios. It is not certain if she will appear in any future Fallout game.
Behind the scenes
In Greco-Roman mythology, Hecate (or Hekate) is a goddess of the Underworld who is associated with magic, witchcraft, and necromancy.