Baile in Scáil, or Eacstais Fháidhiúil an Taibhse (Phantom’s Frenzy (Home in Shadow), or Prophetic Ecstasy of the Phantom). c AD 1050:

‘Baile in Scáil: The Phantom’s Frenzy’ at Academy for Ancient Texts. Ancient Texts Library.
https://www.ancienttexts.org/library/celtic/ctexts/phantom.html