In the interim the Hamitic Fomorians were demanding their annual tribute from the Tuatha De Danann, and to this end they sent their tax gatherers to collect it at Balor's Hill and when they arrived there, Lugh approached them riding on a magnificent horse that belonged to Manannan, the son of Ler, (The Isle of Man was to receive its name from him) and he had on Manannan's breastplate and helmet, and was armed with a sword, a shield and a quantity of poisoned darts. He immediately went into battle against them and by the time he was finished only 9 of the Fomorii were able to escape his fury and he let them go as he wanted to ensure that they would return to their home base on Tory Island and inform the Fomorian Kings how they would be received if they should attempt to come again. Balor of the Stiff Blows on being informed of what had transpired queried, "Who could this outstanding young warrior be," and his wife replied, "He can only be the son of our daughter, Ethniu, as it seems that he has cast his lot with his father's people, and we shall never succeed in Inis Ealga / Ireland again." The Fomorii then held their own counsel, at which Elathan, Indech, Tethra, Breas, Balor of the Evil Eye / Stiff Blows, his wife and 12 sons and their warriors and Druids also attended, to decide what retaliatory action they should now take against the Tuatha De Danann.

    Meanwhile, Lugh had sent his father, Cian to travel throughout Inis Ealga to call on all of the Tuatha De Danann Septs to assemble and make preparations for what would now occur if the Fomorians decided to advance against them. During his travels Cian was to come across Brian, Iuchar and Iucharba, who were 3 of the sons of Tuirenn, who was another of the sons of Ogma. On seeing the 3 brothers in the distance ahead of him he decided to hide out as they passed by, as there was great enmity between them and Cian and his own 2 brothers, Cethe and Cu. Nearby he saw a herd of pigs, and he decided to hide himself within the herd hoping they would not see him as they passed on by, but he soon became aware that they had seen him, and he decided to make a run for it, and they chased after him, and Brian threw his spear at him and he was severely injured and he cried out for quarter. The other two brothers, Iuchar and Iucharba were willing to back off, but Brian was determined to kill him, and Cian cried out to them, "If you kill me there will be a great blood - fine to be exacted for it." Despite his dire warning they still went ahead and killed him, and then buried his body and continued on their way to Tara. Meanwhile, Lugh who was waiting for his father to return from his journey, was alarmed at the amount of time he was taking, so he decided to go and search for him himself, and he eventually traced his whereabouts as far as the Plain of Muirthemne where he was informed by witnesses of what had previously taken place there. He dug up Cian's body to be sure that it was really his father who they had killed and after mourning his loss he reburied his body and set up a pillar stone above the grave with Cian's name inscribed in Ogham there at Ard Chein / Dromslian. Lugh then returned to Tara where he saw the 3 sons of Tuirenn among those already present in the hall and he called an Assembly and asked the question, "What would be the vengeance anyone of you would take upon anyone who had murdered your father." Nuadha their previous leader, declared that they should "Be torn from limb to limb," and all present agreed to this, including the 3 sons of Tuirenn. Lugh then said, "Let no one leave this hall until a blood - fine has been agreed upon," and once again Nuadha replied, "I would consider them to be lucky if you are willing to accept only a fine instead of vengeance." Iuchar and Iucharba were willing to own up to their crime, but Brian was afraid Lugh would naturally not accept just a fine, and he said, "We did not kill Cian, but as we are suspect we would pay the fine to remove any anger towards us." Lugh then informed them of what he would consider to be a reasonable fine, but Brian was still wary of the way he had expressed it, as he seemed to ask too little for what they had done. The 3 brothers then pledged that they would pay the fine willingly, and Lugh gave them his pledge to ask no more of them, only that they bring the spoils he requested back to Nuadha. They then set out on the quests that Lugh had outlined for them and were able to successfully carry out what turned out to be very difficult tasks. During their last task they were to come upon Miodhchaoin who was also a King of the Fomorii who had not only trained his father Cian, but also Lugh himself who was well aware that Miodhchaoin would turn out to be their most formidable foe, but despite this they were still able to kill him during the conflict. Despite this the 3 brothers were then slain in return by Miodhchaoin's 3 sons, Corc, Conn and Aedh who were also feted to die during their final encounter.

      The Fomorians now gathered together all of their ships from the Hebrides, and went to the north coast of Ireland where they landed on the mainland, and then marched to Tir Erril in Co. Sligo in the north - west of the Connacht Province where they waited for the Tuatha De Danann to advance against them. Morrigu informed the Daghda Mor - the Great Father that the Fomorii forces had arrived on the mainland, and with his followers and the Druids they went on to the River Unius in Co. Sligo to confront them hoping to gain more time to prepare for the coming battle. As the Tuatha De Danann were still not quite ready yet the Daghda Mor engaged the Fomorii in a lengthy dialogue  hoping to gain more time and as they received him genially he went about entertaining them and they gave him a meal. (Nuadha of the Silver Hand, the Daghda Mor, and Lugh had previously called a convention of all the learned men from the Tuatha de Danann where they had all resolved to go immediately into battle should it be necessary). When the conflict was to finally occur this was to be the second great battle they would be involved in at Moytura, except that this time it would be against the Fomorii, 50 miles north of the original battle they had previously had against the Fir Bolg, when they had first arrived into Ireland.

    On the eve of Samhain, the beginning of Summer into Winter, the two forces were to finally come face to face in the Battle of Mag Tuireadh na b-Fomorach, as the Daghda Mor had eventually gained enough extra time for the Tuatha De Danann to finally organize their forces after he had intervened personally with the Fomorii to bring this about. During the course of the battle many of the weapons of the Fomorii were to be destroyed and their Champions killed, while the Tuatha De Danann with their bronze weapons continued to gain the upper hand, and the Fomorii were becoming more and more desperate. The Fomorii eventually decided to send Ruadan, the son of Breas and Brigid, who was therefore also a grandson of the Daghda Mor, and he was disguised as a Tuatha De Danann warrior, as they wanted to find out why the Tuatha De Danann were continuing to be so successful against them in the battle. After gaining access to their ranks he came upon Creidne, Gobhan Saer and Luchtaine who he could see were rapidly repairing the Tuath De Danann weapons, as quickly as they were being damaged during the conflicts. Ruadan then returned to the camp of the Fomorii and informed them of what was going on, and they told him to go back and kill Gobhan Saer, so he returned to the Tuatha De Danann position and to this end approached Gobhan Saer asking him for a javelin, and taking it up he speared Gobhan Saer who then withdrew it from his own body and threw it back at Ruadan. Although he was also severely wounded, Ruadan was still able to flee back to the Fomorian lines where he was later to die, while Gobhan Saer had gone straight to the physicians, Diancecht and his daughter, Airmid to be healed.