CHAPTER XII
It is to be known that on the night of the Feast of Samhain the doors separating this world and the next one are opened, and the inhabitants of either world can leave their respective spheres and appear in the world of the other beings.
Now there was a grandson to the Dagda Mor, the Lord of the Underworld, and he was named Aillen mac Midna, out of Shí Finnachy, and this Aillen bore an implacable enmity to Tara and the Ard-Rí.
As well as being monarch of Ireland her High King was chief of the people learned in magic, and it is possible that at some time Conn had adventured into Tir na n-Og, the Land of the Young, and had done some deed or misdeed in Aillen's lordship or in his family. It must have been an ill deed in truth, for it was in a very rage of revenge that Aillen came yearly at the permitted time to ravage Tara.
Nine times he had come on this mission of revenge, but it is not to be supposed that he could actually destroy the holy city: the Ard-Rí and magicians could prevent that, but he could yet do a damage so considerable that it was worth Conn's while to take special extra precautions against him, including the precaution of chance.
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