Complex sentence: He requests that they recite for him the story of the Cattle Raid of Cooley, an Táin Bó Cuailnge they cannot meet his request however because they do not know the tale, nor have they ever heard of it.
Split into simpler sentences: He requests that they recite for him the story of the Cattle Raid of Cooley, "an Táin Bó Cuailnge". They cannot meet his request however because they do not know the tale, nor have they ever heard of it.