Jason was my son,
and today is his birthday...''
-Pamela Voorhees (1980).
Friday The 13th
Pamela Voorhees was the mother of the Legendary Slasher Jason Voorhees. She was driven insane when her only child, drowned in Camp Crystal Lake, due the negligent and irresponsible Camp Counselors.
She heard the voice of her dead son, Jason in her twisted mind. It drove her into a killing rage; she routinely stalked the grounds of Camp Crystal Lake, picking off any unlucky Camp Counselors she encountered. She was determination to see the Camp shut down. Her methods of killing were brutal; driving spears through necks, arrows through heads, and more.
She however met her fate at the hands of the Counselor named Alice. It resulted in a showdown by the lake's edge, where she was decapitated by her own Machete, in front of her drowned son.
She now is the voice of reason, and driving spirit behind her resurrected son, who carries on her wicked legacy.
Freddy VS Jason VS Ash The Nightmare Warriors
After Freddy becomes one with the Necronomicon, Freddy tells Jason he will resurrect Jason's family if the Crystal Lake killer joins Freddy, Jason agrees, and Freddy brings Jason's Mother Pamela, and sister (who Jason killed in Jason Goes to Hell and used her body as a vessel to be reborn in) Jason later walks in on Freddy and his mother Pamela having sex, and Freddy simply says "I'm your new daddy" which leads Jason to despise Freddy even more.