Nissa Nissa

"According to prophecy, our champion will be reborn to wake dragons from stone and reforge the great sword Lightbringer that defeated the darkness those thousands of years ago. If the old tales are true, a terrible weapon forged with a loving wife's heart. Part of me thinks man was well rid of it, but great power requires great sacrifice. That much at least the Lord of Light is clear on."

- Thoros of Myr Nissa Nissa ​was the wife of the legendary hero Azor Ahai. In order to unleash the powers of the sword Lightbringer so that he could defeat the darkness of the Great Other, he had to sacrifice her by plunging the it into her heart.

In the books
In the A Song of Ice and Fire novels, Nissa Nissa was the wife of Azor Ahai.

Darkness lay over the world and Azor Ahai was the hero chosen to fight against it. To fight the darkness, Azor Ahai needed to forge a hero's sword. He labored for thirty days and thirty nights until it was done. However, when he went to temper it in water, the sword broke. He was not one to give up easily, so he started over. The second time he took fifty days and fifty nights to make the sword, even better than the first. To temper it this time, he captured a lion and drove the sword into its heart, but once more the steel shattered. The third time, with a heavy heart, for he knew before hand what he must do to finish the blade, he worked for a hundred days and nights until it was finished. This time, he called for his wife and asked her to bare her breast. He drove his sword into her breast, her soul combining with the steel of the sword, creating Lightbringer.