The Wellspring

They called her the Wellspring. She was born of the Spirits and through her all magic flowed. It was known through the lands that the Wellspring could grant you magic, for a price. An exchange, equivalent in nature to what you offered her, was necessary to keep the balance of her gifts. Some argued that if you had to give her something for it, then the magic wasn’t a gift. Those people were to be ignored, no one should question the Spirits wording.
The Wellspring was happy to share her gift with people. It didn’t much matter to her what she would be offered for it, but the exchange was necessary. A dragon offered her its wings for the gift of fire, a different one offered her its heart for the gift of water. She gave them the magic, and they gave her what she counter-offered, protection and mobility, the loyalty of their species. The raven asked for the gift of speech, she offered an exchange: the magic that would allow everyone to understand him for his feathers. Now she has a cloak.
He offered her love. Claimed He would only love Her, in exchange she gave him access to all of her magic, for there was nothing more valuable to her than love. He lied to her, and thus the curse was born. For an exchange of unequal proportions, misguided and malignant, twists itself back and becomes what you don’t want it to be.
She was the Wellspring, the giver of magic. He became the Cursebearer, the taker of lives. She would not be tricked twice. They say the Wellspring will still give you magic if you ask, but your gift had better be worth it or you risk becoming a Cursebearer yourself. Every gift has a price, they say, and if you try to cheat the Wellspring, you’d wish the price you’d paid was death because that would be more welcome than the Curse she’d leave you with.