"Herein lies the mother's womb, containing the power to create life!"
In the game Silent Hill Dahlia Gillespie was the head of a cult that was created to raise the demonic angel, (or old god), Samael and tap his powers to bring about their own Paradise on earth. Through her studies, she learned that Samael's soul could be trapped within an unborn infant.
She, herself, would be the mother, and Dr. Kaufman, would be the father, to such a child.
After performing the rituals and nine months past, Dahlia gave birth to Alessa. The child was lovely, but there was no motherly love to be had from the woman towards her child. Instead, there was anger. Her ritual and plans partly failed. The Cult Leader only managed to trap only half of Samael's soul in the girl child she had bore.
This was a harsh step back to the cult and Dahlia was left to come up to a solution. She came to the conclusion, she would force Alessa to call her other half or kill her daughter and start again. Working with Kaufman, she badly burned Alessa in a house fire. Sameal's powers semi-awaken and allowed Alessa to live despite the horrible condition of her body.
Realizing it was god's powers keeping her child alive, they kept the half-soul girl in the basement of the hospital with Nurse Lisa Garland tending to her. This, in theory, is when they began to tap her power to distort the town of Silent Hill.
"The demon is awakening, spreading those wings!"
Alessa called upon her other half and waited, just as Dahlia did. Both waiting, plotting, and gathering powers for their deadly game to really begin. One game to own a god; one to be free from a power-hungry sadist.
When Harry Mason came into town with his daughter, Cheryl, the pieces where in place and the game began. Realities broke into three and the struggle began.
Dahlia cleverly lead Harry through the town and armed him with devices to lure out the hiding halves of Samael through the ties of a father and daughter's love. Revealing herself officially to him in a church, Dahlia gave Harry the drawbridge key and the 'Flauros' after warning him that sounds something a kin to a mad woman's rant, urging him to the Hospital.
At the basement of the hospital where Alessa rested, the reunion of mother and child occurred as the final stage of the game is set. Depending how the player played effects the outcome of the final ending, but Dahlia's death is unavoidable.