this is not a happy myth
Mara and Vala created two children together. The younger, nicknamed Sini, was a joy to all who knew her. She particularly loved travelling with her mother in the spring, when she would run ahead to each village that waited for her mother's return. As she grew older, people mistook her for her mother's attendant. When she arrived ahead of her mother, celebrations would be held for her as a harbinger, or even as the one responsible for her mother's return.
It made Sini uncomfortable, but she enjoyed being the center of attention and the way people cheered to see her. In some areas, there were whole feast days just for her, in anticipation of her mother's arrival.
One spring as they journeyed, Sini went ahead to a village that always welcomed her thus, and she expected her mother would be arriving the next day. The villagers cheered her and toasted her long into the night, and this year they had added a bonfire to the celebration. The food was good, the mead was good, the company was good. In the morning, Sini waited with the villagers for her mother to arrive, but unknown to her, Mara had been delayed by an attack by her father's sister, Oc Ha.
As the day wore on, Sini did her best to keep their spirits up, and for a while, it worked. As the third day dawned, however, the villagers were beginning to whisper.
On the fourth morning, the headwoman of the village and a few others greeted Sini outside of the room she'd been given.
"Is the Mara arriving today?"
Sini could only shrug. "I hope so. I'm worried."
"I was afraid you'd say that," the headwoman said. Several larger villagers pushed past her and grabbed Sini, dragging her out into the square. The young spirit was too confused to fight back. There was a small crowd waiting there, and an old woman who was shouting about how spring demanded blood and sacrifice, how they had to order the Mara to return their spring.
The old woman began to tie Sini up, and she could tell the ropes were magic because they held her fast. She was laid across a stone and the old woman began to cut her open. Sini writhed in pain, trying to escape the blade, to no avail. She screamed for her mother, but it was hours before Mara arrived.
The Mara was still dressed for the fight she'd been dragged into in the forest. Her clothing was badly burned and stiff with drying blood. Her hair hung wild. The villagers shook in fear as Mara cut her daughter loose from the stone and then turned to the old woman.
"Shed your lies," Mara demanded, and the old woman shifted, standing up straight and then straighter until she was much too tall to be human, her hair now black and smooth, her skin smooth and moonlike, her eyes narrow with hate.
"Oc Ha, how dare you?" Mara growled. "I had no quarrel with you and your siblings until you took arms against me."
"Your existence pains us," Oc Ha answered, her voice sounding as if she was on the verge of laughter. "Your humans and your children are nothing but playthings. And her, she was bred with one of these local spirits! How can you expect us to ignore that?"
Mara screamed and dove at Oc Ha, her bloodstone sword trailing energy behind it. Oc Ha tried to parry with her knife, but Mara's fury won, driving the older spirit back until she landed a deep cut with her blade. Cursing, Oc Ha fled, and Mara returned to her daughter's body.
Sini was still alive, though faded. Mara took what was left of her energy and reshaped her as a small blue songbird. Bluebird fluttered up and then returned to sit on her mother's shoulder.
Mara looked at the villagers, who cowered. "We were mislead! We're sorry!" they cried. "And she didn't even die! Please, spare us your wrath! We were afraid you would not come!"
"And so you thought to bully me? We work as partners to plant and harvest! You do not control everything, you cannot. The thaw comes when it comes. The vegetables ripen when they choose."
The people nodded.
"Henceforth, you must sacrifice one of your own children to me each year in repayment," Mara told them.
The cry was instant. "But-!"
"My daughter did not die, and I will not always take your children either. But you have asked for a way to call me in, and I will give you what you asked for."
With that, Mara returned to the forest, Bluebird flying beside her.