What was the reason for the Tragic Death of Cenn Obi and the Destruction of Da Thféider’s Hostel? Not difficult that.
There was once a great queen of Alt Da Rann and Leia was her name. War had sprung up between her people and those of Da Thféider. She sent messengers to ask for aid from the wildman, Cenn Obi. He lived in the wilderness far to the west. These were the messengers she sent: Síd Tríphe Óg, who knew all the languages of man and beast, and the dwarf, Artú.
The remainder can be found here, as all men know. In addition the footnotes to this epic relating what not all men know can be found here. For example:
(4) Finn, as the name for Luke, is just a calque. Luke comes from Greek leukos meaning ‘white’, Finn also means ‘white, bright’ in Irish. It also helps that Finn is the name of the hero of the Fenian Cycle, Finn mac Cumaill.
(7) The epithet Aenfer is taken from Art mac Conn. He was called Aenfer (literally 'one man') because in Echtra Chondla his brother, Connla, was taken away to the Otherworld. So he was left alone, or aenfer, or “solo”.