Unfortunately, we do not have any Gaulish Mythology. We cant look to myths to help us gain better insight into the relationships involving the Deuoi and the world around us. This can be hard for some to get involved as some like to usually have some frame of reference about the nature of the Deuoi. As myths can teach a lot of different cultural concepts within them. Now we have plenty of folks in the Greater Gaulish Community that are writing Neo Myths, based on their own interpretations of a Gaulish worldview. There are most likely traces of Gaulish myth in different folklore and legends, and there might be remanence of their myths in other cultures’ myths. One can see traces of myths on Coins, Depictions of the Deuoi, and many of the art-covered artifacts, we have found. Such as the Gundestrup Cauldron, Pillar of the Boatman, and much more items.
That being said, below are some legends or rather hints at some greater mythos of the Senogalatis. Now, these were not written by the Gauls but rather by their neighbors.
From the Darkness
Cæsar, C. J., “De Bello Gallico”, vi, 18, 1
All the Gauls assert that they are descended from the god Dis, and say that this tradition has been handed down by the Druids. For that reason they compute the divisions of every season, not by the number of days, but of nights; they keep birthdays and the beginnings of months and years in such an order that the day follows the night.
The First Gaul
Parthenius, Love Romances, 30
Hercules, it is told, after he had taken the king of Geryones from Erythea, was wandering through the country of the Celts and came to the house of Bretannus, who had a daughter called Celtine. Celtine fell in love with Hercules and hid away the kine, refusing to give them back to him unless he would first content her. Hercules was indeed very anxious to bring the kine safe home, but he was far more struck by the girl’s exceeding beauty, and consented to her wishes; and then, when the time had come round, a son called Celtus was born to them, from whom the Celtic race derived their name.”
The First Gaul
Diodorus Siculus, Library of History, 5.24.1 – 5.24.3
Now Celtica was ruled in ancient times, so we are told, by a renowned man who had a daughter who was of unusual stature and far excelled in beauty all the other maidens. But she, because of her strength of body and marvellous comeliness, was so haughty that she kept refusing every man who wooed her in marriage, since she believed that no one of her wooers was worthy of her. Now in the course of his campaign against the Geryones, Heracles visited Celtica and founded there the city of Alesia,23 and the maiden, on seeing Heracles, wondered at his prowess and his bodily superiority and accepted his embraces with all eagerness, her parents having given their consent. From this union she bore to Heracles a son named Galates, who far surpassed all the youths of the tribe in quality of spirit and strength of body. And when he had attained to man’s estate and had succeeded to the throne of his fathers, he subdued a large part of the neighbouring territory and accomplished great feats in war. Becoming renowned for his bravery, he called his subjects Galatae or Gauls after himself, and these in turn gave their name to all of Galatia or Gaul.”
The great city Lugdunum
Plutarch , Of the Names of Rivers and Mountains, and of the Objects Found Therein , VI:
By the Arar is a mountain which was called Lugdunum, and which changed its name for the cause which I am about to relate. Momorus and Atepomarus, who had been dethroned by Seseroneus, undertook, according to the answer of an oracle, to build a city on this mountain. side, filled the surrounding trees. Momorus, well versed in the science of the augurs, gave the city the name of Lugdunum. For lugus in the language of the country, means crow, and dunus a mountain.
Mighty Rix Ambicatus
Titus Livius (Livy), The History of Rome, Book 5. 34,35
About the passage of the Gauls into Italy we have received the following account. Whilst Tarquinius Priscus was king of Rome, the supreme power amongst the Celts, who formed a third part of the whole of Gaul, was in the hands of the Bituriges; they used to furnish the king for the whole Celtic race. Ambigatus was king at that time, a man eminent for his own personal courage and prosperity as much as for those of his dominions. During his sway the harvests were so abundant and the population increased so rapidly in Gaul that the government of such vast numbers seemed almost impossible. He was now an old man, and anxious to relieve his realm from the burden of over-population. With this view he signified his intention of sending his sister’s sons Bellovesus and Segovesus, both enterprising young men, to settle in whatever locality the gods should by augury assign to them. They were to invite as many as wished to accompany them, sufficient to prevent any nation from repelling their approach. When the auspices were taken, the Hercynian forest was assigned to Segovesus; to Bellovesus the gods gave the far pleasanter way into Italy. He invited the surplus population of six tribes —the Bituriges, the Averni, the Senones, the Aedui, the Ambarri, the Carnutes, and the Aulerci. Starting with an enormous force of horse and foot, he came to the Tricastini.
Beyond stretched the barrier of the Alps, and I am not at all surprised that they appeared insurmountable, for they had never yet been surmounted by any route, as far at least as unbroken memory reaches, unless you choose to believe the fables about Hercules. Whilst the mountain heights kept the Gauls fenced in as it were there, and they were looking everywhere to see by what path they could cross the peaks which reached to heaven and so enter a new world, they were also prevented from advancing by a sense of religious obligation, for news came that some strangers in quest of territory were being attacked by the Salyi. These were Massilians who had sailed from Phocaea. The Gauls, looking upon this as an omen of their own fortunes, went to their assistance and enabled them to fortify the spot where they had first landed, without any interference from the Salyi. After crossing the Alps by the passes of the Taurini and the valley of the Douro, they defeated the Tuscans in battle not far from the Ticinus, and when they learnt that the country in which they had settled belonged to the Insubres, a name also borne by a canton of the Haedui, they accepted the omen of the place and built a city which they called Mediolanum.
Journey to the Otherworld
47 Since I have reached this point in the history, it is necessary for me to record a story which bears a very close resemblance to mythology, a story which did not indeed seem to me at all trustworthy, although it was constantly being published by countless persons who maintained that they had done the thing with their own hands and had heard the words with their own ears, and yet it cannot be altogether passed over lest, in writing an account of the island of Brittia, I gain a lasting reputation for ignorance of what takes place there.48 They say, then, that the souls of men who die are always conveyed to this place. And as to the manner in which this is done, I shall presently explain, having many a time heard the people there most earnestly describe it, though I have come to the conclusion that the tales they tell are to be attributed to some power of dreams. 49 Along the coast of the ocean which lies opposite the island of Brittia there are numerous villages. These are inhabited by men who fish with nets or till the soil or carry on a sea‑trade with this island, being in other respects subject to the Franks, but never making them any payment of tribute, that burden having been remitted to them from ancient times on account, as they say, of a certain service, which will here be described by me.
50 The men of this place say that the conduct of souls is laid upon them in turn. So the men who on the following night must go to do this work relieving others in the service, as soon as darkness comes on, retire to their own houses and sleep, awaiting him who is to assemble them for the enterprise. 51 And at a late hour of the night they are conscious of a knocking at their doors and hear an indistinct voice calling them together for their task. 52 And they with no hesitation rise from their beds and walk to the shore, not understanding what necessity leads them to do this, but compelled nevertheless. 53 There they see skiffs in readiness with no man at all in them, not their own skiffs, however, but a different kind, in which they embark and lay hold of the oars. 54 And they are aware that the boats are burdened with a large number of passengers and are wet by the waves to the edge of the planks and the oarlocks, having not so much as one finger’s breadth above the water; they themselves, however, see no one, but after rowing a single hour they put in at Brittia. 55 And yet when they make the voyage in their own skiffs, not using sails but rowing, they with difficulty make this passage in a night and a day. Then when they have reached the island and have been relieved of their burden, they depart with all speed, their boats now becoming light and rising above the waves, for they sink no further in the water than the keel itself.
56 And they, for their part, neither see any man either sitting in the boat with them or departing from the boat, but they say that they hear a kind of voice from the island which seems to make announcement to those who take the souls in charge as each name is called of the passengers who have come over with them, telling over the positions of honour which they formerly held and calling out their fathers’ names with their own. 57 And if women also happen to be among those who have been ferried over, they utter the names of the men to whom they were married in life. 58 This, then, is what the men of this country say takes place. But I shall return to the previous narrative.
Procopius: The Wars Book VIII.20.47-58
Gaulish Paganism 