From The Lady of the Linden Tree by Barbara Leonie Picard. (This is one I mentioned earlier)

Sir Merewine of the Hill was accounted among the best of all knights, no matter how one chose to reckon it– whether by skill, or courtesy, good looks or good deeds. He was a truly noble man and was adored by many women, but he politely declined all their attentions.

He had sworn to take as his lady only the most beautiful woman in the world, though he did not yet know who she was.

Nevertheless, he served equally any who had need of him. He was not unkind in his determination to choose the loveliest, only set in his mind.

One day, as he was on his way to a midsummer tourney in the Joyous Valley, he passed by the edge of a wood and heard weeping. Being unable to hear the sound of distress without offering his help, the good knight looked about until he saw a young woman under a linden tree, weeping into her hands.

He approached, asking if there were any way to assist her. When she looked up it took all his skill to carefully conceal his disgust, for she, truly, was the ugliest of women.

The lady explained she had three requests to make of some brave knight, but because of her awful appearance she had been unable to find any willing to help her.

“More shame to them,” said Sir Merewine.

He offered to take on her tasks, and asked what they were, but she would only tell one at a time.  The first was a knight Sir Merewine must challenge in her name, in order to bring back his helmet.

Upon meeting the knight, Sir Merewine saw the battle would be hard, but he stood by his word and fought the dark knight until the the larger man fell unconscious under a blow from Sir Merewine.

Having won, Sir Merewine took the fallen knight’s helmet and returned to the lady for the second task.

The lady refused to tell it to him until she had tended his hurts and allowed him to rest.

For his second assignment, Sir Merewine rode to the palace of an enchantress. On her girdle, the Lady told him, she wore an magical mirror that he must break. Sir Merewine felt this would be no hard task, but the Lady warned him that above all he must not look in the mirror himself, or he would forever be the slave of the enchantress.

“Whatever else you forget, for your own sake do not look in the mirror. Rather ride back with it still unbroken and the enchantress’s power untouched.”

The lady’s fears for her knight proved grounded, for, even knowing that she was an enchantress, Sir Merewine found himself captivated. As she fed and flattered him it became harder to deny her repeated suggestions and requests to look in the mirror.

She was truly the most beautiful woman he had ever seen.

“If I search for a lifetime, I shall not find a more beautiful lady. Why should I not look into her mirror and be her slave forever?”

And he took the mirror from the enchantress’s hand, ready to look into it. But then he heard in his mind the anguished voice of the Lady of the Linden Tree:

“For your own sake do not look in the mirror. Rather ride back with it still unbroken and the enchantress’s power untouched.”

With all his strength he took the mirror and smashed it against the corner of the table. Instantly the enchantress and her castle vanished, and the knight stood in an open field with his horse, surrounded by a crowd of cheering people. All had been held by the enchantress’s power and were now free.

Returning to the Lady of the Linden Tree, Sir Merewine saw her smile at his approach. She heard with joy of his escape and success, but all her smiles could make her no less ugly.

Then she sadly shared the third task, allowing it was the most difficult of the three.
The lady asked that he take her on his horse to the tourney, and for the space of three days tell the world that she was his lady, and he, her true knight. After this time, she would leave and he would never have to see her again unless he wished it.

Sir Merewine agreed: this would be the hardest of the tasks. His heart nearly failed him, but he told himself,

It is a great grief for a damsel to have no knight of her own, and it is an even greater grief for her to be so ugly. It will be but for three days, however hard it is, and then it will be over for me. But for her it will be something that she can treasure all her life.

For though she may be ugly, she has a right to happiness, as has any damsel.

And so he did as she asked, though the task seemed greater the closer he drew to the castle in the Joyous Valley. Yet as heavy as his heart grew as he approached, it was even more difficult to enter, and walk among his friends and rivals. He, who had sworn to take none but the fairest lady in the world.

The laughter was very great among both the knights and the ladies, but Sir Merewine’s courtesy never faltered. He treated the Lady of the Linden Tree with honor, and challenged any knight who laughed at her too openly, so that by the second day the mockery of the men was more concealed.

But there was nothing the good knight could do about the abuse of the ladies, many of who would have given all to be his, for words are the only means a knight has to fight a lady, and the words of a courteous knight are no match for the sharp tongues of women.

Through all this abuse the Lady of the Linden Tree held her head proudly among them, and answered not a word to all their railing against her. Sir Merewine admired her for this, and imagined she would have made a valiant knight.

On the evening of the third day, a messenger came from the king and queen bearing a fantastic sword in a jeweled scabbard, and a gorgeous dress. These gifts were to be given to the best knight, and the most beautiful lady of the tourney.

There was no question among the men that Sir Merewine should be given the sword, but the laughter and mockery broke out afresh as the women reminded everyone that this knight’s lady certainly could never be worthy of such a dress. The crowd began again to heap abuse upon her.

But Sir Merewine grew angry and leapt to his feet and cried out in a great voice, “Shame on you all to make jest of one who has never harmed you, but born your insults bravely. I will hear no more such words.”

He turned to where the Lady of the Linden Tree stood silent, and going upon one knee before her, he took her hand in his. “I will bear no more from you,” he said to the assembled company, “for this is my lady, and I am her true knight.”

And in that moment the words were not spoken to keep the promise he had made to her, nor were they said in pity, but he meant them from his heart. He raised her hand to his lips and kissed it.

And to the wonder of all in the room, not the least to the wonder of Sir Merewine himself, the lady he held by the hand was utterly transformed when he looked again into her face.

She was truly the most beautiful of women; so much so that Sir Merewine wouldn’t have believed it were she if he’d not been holding her hand through it all.

The lady explained that this was her true form, but because she rejected the love of the dark knight, his love had turned to anger, and he had partnered with the enchantress to make the Lady of the Linden Tree as ugly as she had been beautiful.

The spell could only be broken if she could find a knight to serve her in those three deeds, ugly as she was. Sir Merewine was the only knight who would do so. She turned to him.

“And so the spell is broken, and for all that you have done for me I thank you with my whole heart. Now, even as you have kept your promises to me, so I shall keep mine to you, and unless you wish it, you shall see me no more.”

But, of course, Sir Merewine realized that he had at last found the woman he’d been looking for for so long.

“Now that I have found her, think you that I shall let her go?

That day, not only did Sir Merewine receive the king’s sword, but the Lady of the Linden Tree was given the queen’s gift, for all found it easy to judge that she was most fair among all the ladies.

Three days later Sir Merewine was wedded to the Lady of the Linden Tree.

And no knight and his lady in all the world could have been happier than they.