Fergus mac Róich
A ninth century "rémscéla" or foretale recounts how the tale came to be. In the 6th century, the poet Senchán Torpéist gathered the poets of Ireland together to see if any of them knew the story of the "Táin Bó Cúailnge", but they all only knew parts of it. His son Muirgen came to the grave of Fergus mac Róich and spoke a poem, and Fergus' ghost appeared to him and related the events of the "Táin" as they happened.