This tale is the power of the Dagda to manipulate time and given the solstice phenomenon where the solstice light penetrates the chamber every year and then returns it to darkness it would seem he is also a sun God fertilizing the earth and bringing it back to life.  His son Oenghus will trick him out of possession of Sid in Broige also using time so the old year gives way to the new. This image is using kerbstone 67 with its S spiral.