There was one power the Dark Lord knew not. That was the power of love. He had not been loved as a child, growing up in a cruel orphanage. He had never experienced love as an adult.
Love, to the Dark Lord, was a mystery. But he knew blood. He understood its intoxicating power. He walked towards the home of Lily and James Potter, not suspecting that the power he so well knew would destroy him this night. He tore down the door easily. James Potter pathetically attempted to protect his wife, urging her to get their child and flee. Voldemort dispatched James quickly. He then went to look for Lily. Lily had rushed to the nursery and picked up her son, clutched him close to her breast. Harry had been crying, but quieted as she cooed over him. She knew there was no escape from the monster. Voldemort would keep seeking them until he found them.
"Oh, my son…there is only one thing I can give to you." Lily said. She heard the monster's footsteps approach.
Lily closed her eyes and drew up her magical energies. She had learned this spell from Molly Weasley who had learned it from her mother. She had never wanted to use it. It was magic as old as the world. It would only work at the moment of her death and she knew death was near. She clutched Harry to her chest.
"Goodbye, my son."
She began to chant to the disir, the mothers of old, whose spirits yet watched over their children. She drew upon the power of her mother and grandmother, all the mothers of the Evans and Potter lines back to Embla herself, mother of all the Germanic tribes whose blood Lily carried. She could feel their power enveloping her and Harry, adding their power to her own. The power of the ancient mothers, whose blood yet flowed through her veins and the veins of her son, drew upwards like a shield around them. Voldemort walked into the room and momentarily took a step back.
"I don't know what powers you drew upon, mudblood, but they will not protect you."
Lily smiled. "You have no idea. You really don't do you? If you strike him now it will end in your undoing."
Voldemort grinned, cruelty twisting his features. "It is you who have no idea. Hand over the boy."
"Never."
"If you hand him over no harm will come to you, Mrs. Potter. I give you my word."
"I would never trust the likes of you."
"Very well."
He raised his wand and shouted the killing curse. She fell down, arms still tight around her son, her sacrifice activating ancient forces beyond Voldemort's understanding. The Dark Lord strode forward. The baby cried.
"You'll be joining your worthless mother very soon." Voldemort hissed. He raised the wand and shot out the killing curse. He only had a second to realize the curse had struck a wall of spiritual power, rebounding and destroying his body instantly.
(A.N-The Disir and Embla are from Norse mythology)