Winifred Sanderson (referred to as "Winnie" by her sisters) is the main antagonist in Hocus Pocus and the sister of Sarah and Mary Sanderson. She is the oldest and most intelligent of the three Sanderson Sisters. She loves her spellbook. Back when she was alive, her lover was Billy Butcherson, but she found out he had an affair with her sister, Sarah. Enraged, she poisoned Billy and sewed his mouth shut with a dull needle so that he could not reveal her secrets even in death.
She sold her soul, and possibly the souls of her sisters, to Lucifer for a spellbook of evil magic, containing a recipe for a potion that would enable them to suck the youth from children and maintain their own. Such a child was Emily Binx from whom they sucked her dry of her youth so that she died of being so dramatically aged.
For this crime, along with their refusal to reveal what they'd done to Emily's brother, Thackery (whom they'd turned into an immortal black cat), the Sanderson sisters were condemned to be hanged, but Winifred warned them that in time, on Hallow's Eve when the moon was full, a virgin would light the Black Flame Candle summon the sisters back from the dead.
Eventually, this prophecy was fulfilled when Max Dennison lit the candle 300 years later. The three Sanderson Sisters then tried to abduct him, his little sister, and his girlfriend in order to suck the lives out of all three of them, specifically Max's sister, Dani. With the help of Thackery Binx and Billy, the three eventually defeated the three witches.
Winifred as an old woman.
Winifred zapping Thackery Binx with her electrokinesis
Winnie and her sisters "share" Emily Binx's life-force