Editing Manannán mac Lir (section)

=== The Pursuit of the Gilla Decair and His Horse ===
As the Gilla Decair, a name also referenced in "O'Donnell's Kern", Manannán appears in the Fenian story "The Pursuit of the Gilla Decair and his Horse". In this tale the Fianna encounter the Gilla on [[Samhain]] while pursuing the hunt through the forests of Ballachgowan in [[Munster]]. The Gilla is described as a gigantic, virile ruffian with black limbs, devilish, misshapen, and ugly, leading a gaunt horse with grey hindquarters and thin legs with an iron chain. Additionally, the Gilla is dressed as a warrior with a convex, black shield hanging from his back, a wide grooved sword at his left thigh, two long javelins at his shoulder, and a limp mantle about him, all reminiscent of Manannan's description in "O'Donnell's Kern". After greeting Finn with a lay that begins, "May the gods bless thee, [[Fionn mac Cumhaill|Finn]], O man of affable discourse&nbsp;...", the Gilla tells Finn that he is a [[Fomorians|Fomorian]] who visits the kings of Christendom to earn a wage, and that his name was given because of the great personal sacrifices he makes on behalf of his retainers. The Gilla then asks Finn if he will hire him as a horseman, to which Finn assents, and then asks to release his horse to graze with those of the Fianna. When Finn grants his permission, the Gilla unbridles his horse to graze with the others and proceeds to mutilate and kill all the horses of the Fianna.

After seeking the Fianna's counsel, Finn tells [[Conán mac Morna]] to mount the Gilla's horse and ride him to death, but though he tries violently to make the horse move, he won't budge. Thirteen other Fianna then mount the horse in an attempt to weigh the horse down as much as the Gilla, but still the horse refuses to budge. The Gilla then tells Finn and the [[Fianna]] that were he to serve the rest of his term under Finn's contemptuous frivolity, he would be pitied and mocked, so he tells them that he will be parting, and leaves the [[Fianna]] with such a fierce, thundering rapidity that it is compared to the speed of a swallow and noise of a March wind over a mountain. As soon as the Gilla's horse loses sight of his master, he speeds off after him with fourteen of the [[Fianna]] on his back. Finn and the remaining Fianna then track the Gilla and his horse until they arrive at the sea, where another of the Fianna grabs the horse's tail as it alights over the water with the fifteen men.

Finn then travels to Ben-Adar, where the [[Tuatha Dé Danann]] promised the [[Goídel Glas|children of the Gael]] that should they ever need to leave Ireland, they would encounter a ship outfit for them. As the Fianna approach the sea, Finn encounters a pair of men, described as "bulkiest of heroes, most powerful of fighting men, hardiest of champions". Both men bear shields with lions, leopards, and griffins, "terrible" swords, crimson cloaks with gold fibulae, gold sandals, and gold bands on their heads. They bow to Finn and tell him they are the sons of the King of India, who have the ability to create ships with three fells of the axe and can carry the ships over land and sea. One of the brothers tells Finn that his name is Feradach.

After three days on [[Feradach|Feradach's]] ships without seeing any land or coastline, the Fianna reach a craggy island where they spot the Gilla's tracks. Here it is determined that [[Diarmuid Ua Duibhne|Dermot]], who was fostered by Manannan and Aengus Og, is shamed into vaulting onto the island using the javelins of Manannan, which he possessed. Dermot leaves the Fianna behind and ventures a beautiful forested land, filled with buzzing bees and birds. In the midst of the forested plain, Dermot beholds a massive tree with interlacing branches, beneath which is a well of pure water with an ornamented drinking horn suspended above it. Dermot lusts after the water in the well, pursues it and is confronted with a loud rumbling noise indicating that none should drink of its waters. Dermot drinks the water, and a hostile wizard appears who upbraids Dermot for roaming his forests and drinking his water. Dermot and the wizard battle each other, and the wizard jumps into the well, leaving Dermot behind. Dermot then kills a stag with his javelin, cooks it, and falls asleep. The next day, he finds the wizard, and the two continue their fight for three days with the wizard jumping into his well at the end of each day. On the third day, Dermot follows the wizard into the well and finds upon his emergence, a wide open flowery plain with a regal city. He follows the wizard into the city where he fights the host until he is bleeding, injured, and on the ground. When Dermot awakens, a burly wizard kicks him in the back and explains that he is not there to do Dermot harm but to explain that he is in a dangerous place of enemies. The wizard then takes Dermot on a long journey to a towering fortress, where his wounds are healed with herbs, and he is taken to feasting with the wizard's men.

When Dermot asks where he is and whom he is, the wizard tells him he is in [[Tír na nÓg|''Tir fo Thuinn'']], that he is the Wizard of Chivalry who is an enemy of the Wizard of the Well, with whom Dermot had fought, and that he was hired o work under Finn for a year. While Dermot is detained with the Wizard of Chivalry, Finn and the Fianna craft rope ladders and also scale the cliffs onto the island. There they encounter a king on horseback who takes them to his kingdom where they enjoy feasting. The Fianna wage war with the king against the King of Greece, who is attempting to invade the island. After winning the war, there is a great celebration with the kings of other lands, and there Finn is reunited with Dermot. Dermot explains that the Gilla's true name is Abartach son of Allchad, and he lives in the Land of Promise.

The daughter of the King of Greece promised herself to Finn prior to the King's defeat, so the Fianna split into groups again, one to pursue Abartach, and the other to Greece. The Fianna retrieve the King of Greece's daughter Taise for Finn, and return to the Land of Promise. There they reunite with Finn, who has found Abartach. Abartach challenges Finn to determine what debt is owed for the long journeys, adventures, and victories of the Fianna, to which Conan demands payment in the form of fourteen women from the Land of Promise along with Abartach's own wife, who are to ride on his horse, as the Fianna had, back to Ireland. Abartach agrees to the terms, vanishes before the Fianna, and the company returns to Ireland.

Although none of the characters in the story are explicitly called Manannan, the setting of the tale in ''Tir fo Thuinn'', the use of the name Gilla Decair, which is explicitly one of Manannan's bynames in O'Donnell's Kern, and the description of the Gilla's behavior all clearly point to his being the central character on the island.<ref name="Gilla" /> Additionally, the name Abartach is used in the context of Manannan's family as the right-hand man of Manannan's son Eachdond Mor.<ref name="dobs-altram" /> In the ''Book of Lecan'' Abartach and Manannan are listed together as two celebrated chiefs of the Tuatha De known for being, respectively, a great musician and a great navigator.<ref>{{harvp|Borlase|1897|p=826}}, citing the [[Book of Lecan]]</ref>{{full citation needed|date=July 2024|reason=Borlase's is a 3-volume work, so the vol. no. is needed.}} Elsewhere Abartach, whose name means dwarf, and who also goes by the name Averty, was a magician of dwarfish size that terrorized part of Ireland. Abartach was only vulnerable in one part of his body, and [[Fionn mac Cumhaill]] was able to slay him by sticking his thumb into his mouth to determine the vulnerable spot before spearing him. Abartach was then buried upside down in his grave to prevent his rising from the dead.