Written for Yuletide 2017.

This is set (more or less) during the Fourth Branch of the Mabinogion (Math Son of Mathonwy). From the Book of Taliesin, it's mostly based on Kat Godeu (The Battle of the Trees), but there are also references to Preiddeu Annwfn (The Spoils of Annwvyn), Kerd Veib am Llyr (Song Before the Sons of Llyr), Daronwy, and Kadeir Kerrituen (The Chair of Cerridwen).

"Meanwhile the nephews [Gwydyon and Gilvaethwy] did not return to the court but continued their circuit of the land until Math forbade anyone to give them food or drink. At first they would not return, but finally they came."

-The Mabinogion, "Math Son of Mathonwy" (translation by Jeffrey Gantz)

The men of Dyved buried Pryderi near the Yellow Ford, where he fell in combat with Gwydyon son of Don. There was nothing else left for them to do, since they were defeated in battle and had lost their lord. They set off on the southward journey towards home, lamenting bitterly.

Then Math, the lord of Gwynedd, ordered the hostages to be brought before him, who had been surrendered during the battle. He had no more need of them, since the men of Dyved were dejected and had no more heart to fight. They brought Gwrgi Gwastra, the chief of the hostages; he was the nephew of Pryderi's wife Kigva.

Math sat in the midst of all his lords and pages and warriors with their weapons. His hair and beard were white, but there was great strength in him; he was like a mountain with a snowy peak, or an old apple tree covered with snow. His nephews, Gwydyon and Gilvaethwy, stood beside him.

When Gwrgi Gwastra was brought before him, Math ordered him to be released. "You are free to go," Math said, "and the other hostages with you. The men of Dyved are withdrawing back home, and you may follow after them." There were twenty-three young men, sons of nobles, in addition to Gwrgi.

"Lords, tell me one thing," Gwrgi said. "Which among you is Gwydyon son of Don?"

Gwydon stepped forward from his place at Math's side and said, "I am Gwydyon." His voice was rich and deep; it was easy to tell that he was a great singer.

For a moment a fierce look flashed in Gwrgi's eyes, as if he would have attacked him even without weapons. But he bowed stiffly and said, "Lord, if you permit it, I will return to Dyved."

At Math's order, the men who were guarding him let him go. At that moment, a hound bounded up to them. He was a fine hound, happy and healthy and intelligent-looking. He trotted up to Gwrgi and licked his hand.

"Is that your hound?" Gwydyon asked him. "He is of an unusual kind."

"No," Gwrgi said, "this hound belonged to Pryderi. A lord sent the hound to him as a gift of friendship. But I am surprised to see the hound here. I thought Pryderi left him behind in Rhuddlan Teivi, when he went to war."

"If the hound belonged to Pryderi, you may take him with you."

And Gwrgi went, the hound following along behind him. He and the other hostages returned back to the land of Dyved.

In his camp, Math son of Mathonwy set things in order with the army. When that was done, he said to Gwydyon and Gilvaethwy, "I will now return to Caer Dathal. Will you return with me, or will you make a circuit of Gwynedd?"

Gwydyon said, "Lord, we will make a circuit of Gwynedd and see what has been harmed by the war." Therefore when Math set out for Caer Dathal with his host, Gwydyon and Gilvaethwy remained behind with a small band of followers. They rode southward to begin travelling through the cantrevs of Gwynedd.

But they had gone less than a day's journey before messengers from Math came to summon them back to Caer Dathal.

Gwydyon said to the messengers, "There are many fields and towns that have been harmed by the war, and some of the bridges have been broken down. Say that we will return when we have finished riding the circuit of Gwynedd."

When the messengers had left, Gilvaethwy said, "Why should he summon us back to Caer Dathal so soon?"

"Perhaps Goewin has told him what happened."

Gilvaethwy laughed as if he wished to appear unconcerned. "Why should she tell him? It would only cause her shame to no purpose."

"I did not think she would tell him. But if she tells Math or he discovers it, it will be better for us to be away from Caer Dathal. If Math is angry, we will give time for his anger to cool. We are lords of Gwynedd and his close kin; if he punishes us publicly it will shame him also."

They rode to the southern part of Gwynedd, to be away from Math in Caer Dathal. They continued making the circuit of Gwynedd, but took care that they never came near the court.

When they had been travelling for a week, it happened that they were near the house of a farmer as night was falling. They approached the house, thinking they would stay the night.

The farmer and his wife came out. They bowed low to Gwydyon and Gilvaethwy. "Lords, we are sorry. Math has sent word from Caer Dathal, strictly commanding that no one is to give you food or drink or shelter for the night."

Gwydyon said, "If that is what Math has ordered, then you must obey it."

They camped that night in the woods, and the next day Gilvaethwy said, "Let us ride to the next cantrev; perhaps they have not heard of Math's command." But the next day the same thing happened; the people of the next cantrev had all been ordered not to give them food or drink.

Their men looked at each other. Gwydyon said, "That is no matter. It is high summer; we will hunt and fish, and we will not go hungry. There is no need to return to Caer Dathal."

They arose in the morning and made ready, but they had ridden only a little way when they heard the sound of a hunting horn.

"That horn has a mournful sound," said Gilvaethwy.

"If we are hunting in these woods," Gwydyon said, "why should not others hunt also?"

They rode on, but soon they heard the horn again from behind them. "Let us ride faster," said Gwydyon. They went onward, but soon they heard the horn again, from in front of them. They looked through the trees, which were green with summer leaves, but they saw no one.

And then between one breath and another, a great host stood near them, armed for battle, as if they had sprung up from the ground. Gilvaethwy let out an exclamation and reached for his sword. "Who are they? Some of Pryderi's people who have recovered their courage?"

"I do not think so," said Gwydyon. "There is some enchantment here." He rode forward and called, "Warriors, who are you and who do you serve?"

And one of them, who appeared to be a nobleman, came forward and said, "We serve Arawn King of Annwvyn."

"And have you come here to fight?"

"Between God and me, we have. It is to seek you and for no other reason that we have come so far out of our own land."

"For what reason?" Gwydyon inquired. "For I know of no wrong I have done to Arawn or his people, neither I nor my brother here nor our lord Math."

And the one who served Arawn said, "Pwyll lord of Dyved was the friend of our lord, and so was his son Pryderi. Our king Arawn gave them many gifts, hounds and hawks and horses, and received gifts in return. Among these gifts were the small animals called swine, which came from Annwvyn and which are found nowhere else in Prydain-but you tricked Pryderi into giving them up in exchange for false trinkets and illusions. And when Pryderi came to do battle, it was you who killed him at the Yellow Ford, not many days since. Do you deny these things?"

"It is true that I killed Pryderi," Gwydyon said, "but it was in a fair fight. He challenged me to single combat before both our armies."

"If you had fought him and defeated him only with skill and strength, I would have said nothing! But you also used magic and enchantment against him, and so you were the victor. Because of this, Arawn has come against you."

"It would be a shame for brave men to lose their lives, whether ours or yours. Will Arawn take gifts in compensation?"

"He will not take gifts, for the way you acted was shameful and unworthy of a noble chieftain."

"If Arawn will choose some champion to fight for him, or if he wishes to come himself, I will meet him in single combat, and let us settle it that way."

"He will not send a champion, nor will he meet you himself, for your actions are not honorable. But he will take you prisoner, and you will be chained in Caer Sidi, where nine streams of the ocean flow around the rock, where twilight and darkness are mixed together."

"If Arawn wants me, he will have to catch me. And I think that will not be easy." And Gwydyon went back to the others.

"What is your plan?" asked Gilvaethwy. "I am ready to fight, and so are all our men here, but we have only a small band against their army. Can you call up a false seeming of an army by enchantment?"

"Not against Arawn," Gwydyon said. "He would not be deceived by such a thing."

"Then what will we do? We will defend ourselves as long as we can, but they are enough to kill us all or to take us prisoner, and that would be shameful."

"Do not be troubled," Gwydyon said. "There is enough of an army here to fight against them."

Their men said, "Lord, we are ready to fight. But whatever you will do, do it quickly, since they are making ready for battle."

Gwydyon went among the trees that stood nearby. And Gwydyon said, "I have been the oak and the leaf of the oak; I have been a drop in a shower of rain, I have been the water that nourishes the roots and the earth itself. I have gone deep into the earth in winter sleep and I have sprung up again; I have been a blade of grass in the field, I have been the bee and made honey in cells of wax. I have been the hare and the hound, I have been the fire and the smoke that rises up from it; I have been the sparks struck from the anvil and I have been the blade of steel; I have been the harper and the string of the harp. I am Gwydyon son of Don of the land of Gwynedd. Rise, you trees, arise, all you bushes and flowers, and answer to my command!"

And so great was Gwydyon's power of enchantment that the trees swayed in their places and all turned towards the enemy, and then they slowly uplifted their great roots from the ground and moved into formation, standing against Arawn's host.

In good time the trees reached their position, for the warriors of Arawn's host were almost upon them. Gwydyon and Gilvaethwy and all their men took up their weapons and prepared to receive the attack.

It was a fierce battle; both men and trees fought bravely. The great trees stood firm like a wall and struck with their branches like heavy clubs; none could withstand their great strength. The small trees speared men with sharp points, and the vines and briars twined around their feet and pulled them down. The alder trees stood in the forefront of the battle, with the willows behind. The cherry trees became angry when they were poked with spears, and they quickly displayed their wrath. The elms were very valiant; they held their place in the battle-line no matter how many warriors came against them. Arawn's men shouted that the birches were covering them with their leaves and that the branches of the oak ensnared them.

Gwydyon stood on one side of the battle and Gilvaethwy on the other, to encourage their men and give them heart. They struck many blows against Arawn's host. With the trees' strength helping them, the men of Gwynedd were able to hold off the enemy and even began to push them back.

Then a champion of giant size came out from the ranks of Arawn's men. He was all clad in dark armor and a helmet hid his face; he carried a great axe. He was much taller and stronger than ordinary men; he was able to grasp even the largest trees and toss them aside like kindling. The great trees closed ranks against him and intertwined their branches, but still he forced his way through. The strong vines wrapped themselves around his feet, but he broke their bonds easily. Onward he came through the battle lines, and no one, however skilled, could stop him.

Gilvaethwy saw him first and shouted a warning to Gwydyon. "Brother, you must stop this champion of theirs or we will all be lost! Can you not fell him with some enchantment?"

Gwydyon could not turn his head to see Arawn's champion, since the battle was too busy on his own side. He said, "The power of Annwvyn is also strong. I can do nothing against him unless I know his name. But if I had that, I could take away all his strength."

Gilvaethwy said, "But his face is covered, and I do not know how to guess his name." All the time they were speaking, the giant man was coming closer, and Arawn's warriors took heart and poured forward into the gaps he made.

Gwydyon said, "Tell me anything you notice about him."

Gilvaethwy said, "I cannot think of anything, except that he has a sprig of alder on his shield."

Then Gwydyon laughed. The giant man had forced his way through the trees and even through the ranks of Gilvaethwy's war-band, although they did all they could to stop him and put their bodies between him and their lord. He raised his axe. In a few steps he would have been close enough to strike Gilvaethwy. But Gwydyon said, "The nephew is a shield to his uncle; high was the hall built in Ireland. You are Bran son of Llyr." And at once the giant's strength left him; his axe wavered in his hand, and he had to retreat back to Arawn's lines. All the men who had followed him were dismayed and fell back with him, while the men of Gwynedd were heartened.

"What is the meaning of the alder?" Gilvaethwy asked. He was leaning on his sword to recover his breath.

"Gwern means 'alder,' and that was the name given to Bran's nephew, the boy who his sister Branwyn bore to the king of Ireland. He put an alder-twig on his shield because of this."

Now it was beginning to get dark, and the two armies broke off fighting for the night. Gwydyon said, "Let us go north a little if we can. The closer to Caer Dathal, the safer we will be." So they left the trees to screen their movements and travelled north as far as they could, and then they made camp and rested for a little. But their sleep was disturbed, for they heard dogs howling in the night.

Dawn was just beginning to break in the sky when Gwydyon awoke. He said to Gilvaethwy, "Lad, go and see if that host is still pursuing us."

Gilvaethwy climbed a ridge and looked down it, and there was Arawn's army making ready to fight with weapons and banners, but all of them completely silent. He came back again to Gwydyon and said, "They are still there, and their number is very great."

"Do not be troubled by that," Gwydyon said. "If there is an army, I will call up another army to fight against them."

Gwydyon took his harp and he went among the trees and sang to them. A strange but beautiful music came from the trees in turn; as beautifully as a wooden flute when a man sends his breath through it, as beautifully as a wooden harp resounding in the hands of a skilled bard, so beautifully sang the trees before Gwydyon. The oak and the thorn-bushes sang in harmony, and they harmonized marvelously well together. As they sang, they pulled their roots from the earth and turned themselves toward the enemy, and they put themselves in battle array as neatly as any host of men. Gwydyon bade them go forward, and they advanced upon the enemy with great lumbering strides. Gwydyon and Gilvaethwy too, and all their men, armed themselves and again made ready for battle.

Arawn's warriors advanced, but this time the leader of their battle-line was a woman. She was beautiful to look upon and rode a fine white horse, wondrously swift, like the sea-mew that skims across the waves and never touches the shore.

The lady on the white horse began to sing, and as she sang all kinds of birds descended to her in flocks. There were strong eagles and swift falcons, small darting songbirds and ravens with stout beaks. All of the birds sang and screeched and cawed and croaked in their own tongues, so that a great din arose; but she restrained them and made them sing in harmony even more beautiful than the song of the trees.

At her signal, the birds flew into battle. Their wings carried them above the trees, so their defense was useless. Then the men of Gwynedd were hard-pressed. The larger birds struck at them with sharp beak and talons; the swans beat at them with great blows of their wings, and the smaller birds flew into their faces and pecked at their eyes, and since they were small and swift it was difficult to come to grips with them. The birds attacked the trees also: they plucked at the leaves with their beaks until the elms and alders were as bare as trees in winter, and they ripped apart the vines with their beaks and claws. A flock of woodpeckers came also and pecked at the aspen trees with their sharp beaks until they were full of holes and had to retreat.

Then the lady called aloud and sent a bird of wrath against Gwydyon. Its wingspan was as great as the length of a spear, and its claws and beak were of iron. Gwydyon fought against the bird from dawn until noon, until at last he was able to strike it down.

Gilvaethwy said, "Brother, use your magic and enchantments and do something about these birds! You can see our men are getting the worst of it." Some of their men had tried to shoot the lady with arrows, but her white horse was so swift that it outran the arrows and not one of them came near her.

Gwydyon looked upon the lady who rode the white horse, and he said, "Your white horse is swift, but speech is swifter. You are Rhiannon, daughter of Heveydd the Old. Let all the birds scatter to the winds!" But for all that, the birds did not cease flying at the men of Gwynedd and attacking them.

The lady on the white horse said, "If I had compelled the birds to fight for me by magic power and enchantment, then indeed they would be driven away. But the birds sing for me and fight for me out of love. I did not constrain them, but I asked them. Pwyll learned that lesson, but you have not-you force the trees and flowers to obey you with a bard's power, and you think everything that grows from the earth is yours to command. If you force things to be what they are not, then they will find a way to twist away from you. I think that will bring you trouble someday."

Gwydyon said, "Why should we fight with birds and trees? Send away your birds, and I will release the enchantment from the trees, and let the two of us fight together."

"Gladly. I am not afraid to face you, dishonorable as you are."

But Gwydyon's men said, "Lord, it does not befit your honor to fight against a woman."

And Gilvaethwy said, "Do not go down to her! Perhaps she will trap you and slay you by some enchantment. If anything happens to you, we are all lost." And so Gwydyon did not go down to fight her.

The battle was very fierce, between the warriors and the enchantments on either side. But at last it became too dark to fight. The birds all flew away to their perches, and the men of both sides withdrew to their own lines.

"Between God and me," said Gilvaethwy, "if night had not fallen, I do not know if we would have lasted much longer against those birds. Let us hope she will not send owls against us!"

"Do not fear that," said Gwydyon. He made a salve of herbs and tended the scratches on Gilvaethwy's face from the beaks and claws of the birds, and then he tended to all their men likewise and treated their wounds.

They did not sleep well that night, since they heard the howling of hounds nearby, and from time to time they could see bright eyes glinting in the darkness through the trees. In the morning, they arose and prepared for battle. They saw Arawn's host in battle array, though Arawn's people did not use trumpets to call their host together but advanced in silence when a banner was raised-that was their custom.

Gwydyon called forth the trees, and they came forward. He also called upon the smaller plants and bushes that stand low to the ground. The rose-briars and raspberry bushes with sharp thorns formed a circle of defense; the gorse stood with its prickles to catch at hands and feet, beside the broom plant crowned with yellow flowers.

Once again the armies came together. While they were fighting, a tall and beautiful woman dressed in grey and brown came forth from Arawn's ranks. Her voice was as powerful as Gwydyon's, and she spoke words of enchantment. Wherever her voice was heard, winter came over the land, although it was the middle of summer. The leaves on the trees, that had been growing fresh and green, turned brown and withered and fell to the earth; frost covered the ground and all the grass withered also. Snow began to drift gently down from the clouds, and where it touched, everything fell into sleep. The trees drowsed and became rooted to the ground where they were. Even the men of Gwynedd were seized by a strong desire to sleep; they swayed on their feet, and Gwydyon had to shout at them and shake them to keep them upright.

Gilvaethwy rubbed his eyes and held his eyelids to keep them open. "Brother, if you cannot do something soon, we are all done for. I will speak to this woman and ask who she is." He went forward and called to her, "Lady, who are you, and why do you send your enchantments against us?"

She answered him, "I dwell with Arawn King of Annwvyn. When Pwyll stayed in our hall, he treated women with courtesy. He was a good companion during the day, but at night he did not touch me or dishonor me in the least, though he had the shape and appearance of my husband and could have done what he wished. But you, Gilvaethwy and Gwydyon, have acted far otherwise! I do this out of friendship for Pwyll and Pryderi, and for the honor of the land of Annwvyn, and out of compassion for the maiden in Caer Dathal who you have wronged."

Gilvaethwy was dismayed. He went back to Gwydyon and said, "How does she know all this? And who is she?"

Gwydyon said, "She is Arawn's wife, the Queen of Annwvyn."

Gilvaethwy said, "Can you not undo her enchantments?"

"I cannot, unless I know her name."

"But do you not know it?"

Gwydyon said, "I do not."

And again battle was joined, and the men of Gwynedd could barely defend themselves. Only the pines and the holly were still ready to fight; all the other trees had gone to sleep.

Gilvaethwy said, "We have had the worst of it in three days' battle. There is no shame in retreating before enchantment and magic. Let us go back to Caer Dathal."

They started to retreat, but it was difficult with Arawn's host following them and harassing them and shooting arrows at them.

Gwydyon called on his power and enchantment and said, "I have been a water-drop in a rainstorm; I have been the ninth wave of the sea. I have been gold and iron; I have been metal gleaming and molten-hot. Let a river arise between us and Arawn's host!" And a river arose out of the earth, with swift rushing waters. It was so deep and wide that Arawn's men could not cross.

As the men of Gwynedd looked back across the river, they saw three figures on horseback ride up. One was a lord tall and strong, with two hounds at his side that were shining white with red ears; the second was the lady clad in grey and brown, who had set the enchantment of winter upon them; and the third was the lady on the swift white horse.

Gwydyon said to the lord, "It is late to show yourself."

Arawn said, "I have been in the battle, though you did not see me."

Gwydyon said, "This fighting is not either to our advantage or yours. Let there be peace between our lands. If we have wronged you, then we will pay compensation."

Arawn said, "There is no need. You will pay, if not to me. Though you twist and turn and change your shape, I think someone will put you in a shape that you cannot get out of."

The lady at his side said, "You raised the trees and plants against us, compelling them by enchantment. Do not make such enchantments again, or I think it will not turn out well for you."

The lady on the white horse said, "Much sorrow and anxiety I had over my son, before I could raise him to manhood. He died through your trickery, and he lies buried in the land of Gwynedd. I will set this fate upon you: that you will know sorrow and anxiety over a child of your blood, and go seeking him through all the cantrevs of Gwynedd."

Gwydyon said, "I have no child yet, and I will do as seems best to me."

Arawn said, "Go back to Math. He will know how to deal with you."

The men of Gwynedd turned and began the journey back north to Caer Dathal. They were well glad to leave that place. The enchantment of winter followed them all along their journey. Wherever they passed, the trees became bare and leafless, a cold wind blew around them, and the ground was covered with snow and ice. It did great harm to the fields that were already damaged from being ridden over during the battles between Pryderi's men and the men of Gwynedd.

They suffered much on the journey, since Math's people were forbidden to give them food or drink. Between the wind and snow, they were not easily able to hunt.

At last Gwydyon and Gilvaethwy and their followers reached Caer Dathal. As soon as they dismounted and their feet touched the ground, the enchantment vanished. The frost melted away and the air was warm, the trees were covered in green leaves, and the birds sang cheerfully. Yet Gwydyon shivered as they turned to enter the castle gate. They dismissed their followers and went inside to face the judgement of Math son of Mathonwy.


The title is from a line in "The Battle of the Trees."

Gwrgi Gwastra: He's mentioned in a couple of lines as one of the hostages Pryderi gives to Math in "Math Son of Mathonwy." He's the only one of the hostages who is named, which makes me think he must be important somehow. Evangeline Walton, in her series based on the Mabinogion, makes him Pryderi's son (though without any source for it, as far as I know). I made him Pryderi's nephew, also without any source, because it seemed thematically appropriate.

Bran and the guessing of names: The notes to Lady Charlotte Guest's translation of the Mabinogion include a passage about the Battle of the Trees from Peniarth MS 98B. It's described as a battle between Amathaon son of Don and Arawn King of Annwvyn caused by Amathaon's theft of three animals from Arawn. "And there was a man in that battle, unless his name were known he could not be overcome; and there was on the other side a woman called Achren, and unless her name were known her party could not be overcome." Gwydyon son of Don correctly guessed that the man was Bran because of the alder sprigs on his shield (since Gwern, the name of Bran's nephew, means "alder") and therefore was victorious. I used parts of this story, though not all of it.

The battle between the men of Gwynedd and Rhiannon's birds came from a line in "The Chair of Cerridwen" about Gwydyon doing battle with "the bird of wrath," but it was also influenced by the surprisingly destructive battle between Owein's ravens and King Arthur's pages in "The Dream of Rhonabwy" from the Mabinogion.