=== アルスター・サイクル ===
モリガンが個人として描かれる最初の物語<ref name="CELT-Regamna">http://www.ucc.ie/celt/online/G301005/text002.html, Táin Bó Regamna, Corpus of Electronic Texts Edition, page33</ref>はアルスター・サイクルの物語で、英雄クー・フーリンと曖昧な関係を築いている。「リーガマインの牛追い」(Táin Bó Regamna、"The Cattle Raid of Regamain") では、クー・フーリンはモリガンに遭遇するが、彼女が自分の領域から雌牛を追い出すので、彼女を認めることができない。この挑戦と、主権者としての彼女の役割に対する自分の無知から、彼は彼女を侮辱した。しかし、彼に襲われる前に、彼女は近くの枝にいる黒い鳥になった。クー・フーリンは彼女が誰であるかを知り、以前から知っていれば、敵対して別れることはなかったと告げた。そして、モリガンは「クー・フーリンが何をしたにせよ、不運を招いたのは確かだ。」と指摘した。そして「あなたには手を出せない。」と言うクー・フーリンに、モリガンは次々と警告を発し、やがて来る戦いで彼が殺されることを予言した。では、クー・フーリンはモリガンに遭遇するが、彼女が自分の領域から雌牛を追い出すので、彼女を認めることができない。この挑戦と、主権者としての彼女の役割に対する自分の無知から、彼は彼女を侮辱した。しかし、彼に襲われる前に、彼女は近くの枝にいる黒い鳥になった。クー・フーリンは彼女が誰であるかを知り、以前から知っていれば、敵対して別れることはなかったと告げた。そして、モリガンは「クー・フーリンが何をしたにせよ、不運を招いたのは確かだ。」と指摘した。そして「あなたには手を出せない。」と言うクー・フーリンに、モリガンは次々と警告を発し、やがて来る戦いで彼が殺されることを予言した。モリガンは「私がいるのは汝の死を看取るためであり、私はそうなるであろう。」と告げた<ref>"[http://www.maryjones.us/ctexts/regamna.html The Cattle Raid of Regamna]", translated by A. H. Leahy, from ''Heroic Romances of Ireland'' Vol II, 1906</ref>。
The Morrígan's earliest narrative appearances, in which she is depicted as an individual, are in stories of the [[Ulster Cycle]], where she has an ambiguous relationship with the hero [[Cú Chulainn|Cúchulainn]]. In the ''[[Táin Bó#Tains|Táin Bó Regamna]]'' ("''The Cattle Raid of Regamain''"), Cúchulainn encounters the Morrígan, but does not recognise her, as she drives a [[cow|heifer]] from his territory. In response to this perceived challenge, and his ignorance of her role as a sovereignty figure, he insults her. But before he can attack her she becomes a black bird on a nearby branch. Cúchulainn now knows who she is, and tells her that had he known before, they would not have parted in enmity. She notes that whatever he had done would have brought him ill luck. To his response that she cannot harm him, she delivers a series of warnings, foretelling a coming battle in which he will be killed. She tells him, "It is at the guarding of thy death that I am; and I shall be."<ref>"[http://www.maryjones.us/ctexts/regamna.html The Cattle Raid of Regamna]", translated by A. H. Leahy, from ''Heroic Romances of Ireland'' Vol II, 1906</ref>
In the ''[[Táin Bó Cúailnge]]'' ("''The Cattle Raid of Cooley''"), Queen [[Medb]] of [[Connacht]] launches an invasion of [[Ulaid|Ulster]] to steal the bull [[Donn Cuailnge]]; the Morrígan, like [[Alecto]] of the Greek [[Erinyes|Furies]], appears to the bull in the form of a crow and warns him to flee.{{sfn|O'Rahilly|1976|p=152}} Cúchulainn defends Ulster by fighting a series of single combats at fords against Medb's champions. In between combats, the Morrígan appears to him as a young woman and offers him her love and her aid in the battle, but he rejects her offer. In response, she intervenes in his next combat, first in the form of an eel who trips him, then as a wolf who stampedes cattle across the ford, and finally as a white, red-eared heifer leading the stampede, just as she had warned in their previous encounter. However, Cúchulainn wounds her in each form and defeats his opponent despite her interference. Later, she appears to him as an old woman bearing the same three wounds that her animal forms had sustained, milking a cow. She gives Cúchulainn three drinks of milk. He blesses her with each drink, and her wounds are healed.{{sfn|O'Rahilly|1976|pp=176–177, 180–182}}<ref>{{cite book |first=Cecile (ed & trans) |last=O'Rahilly |url=http://www.ucc.ie/celt/published/T301035/index.html |title=Táin Bó Cualnge'' from the Book of Leinster'' |year=1967|pages=193–197}}</ref> He regrets blessing her for the three drinks of milk, which is apparent in the exchange between the Morrígan and Cúchulainn: "She gave him milk from the third teat, and her leg was healed. 'You told me once,' she said,'that you would never heal me.' 'Had I known it was you,' said Cúchulainn, 'I never would have.'"<ref>{{cite book |first=Ciaran |last=Carson |title=The Táin: A New Translation of the Táin Bó Cúlailnge |year=2007 |page=96}}</ref> As the armies gather for the final battle, she prophesies the bloodshed to come.{{sfn|O'Rahilly|1976|pp=229–230}}