On the next day Conor and the Ulstermen met him, but a great force of the men of Leinster was also marching from Naas to the border, to recover their womenfolk, even as Atharna had expected.  The Leinstermen then broke the battle on the company from Ulster, and defeated them, driving them with the cows of Atharna on to the sea cape of Ben Edar (Howth), but they recovered the women.  On Ben Edar did King Conor with the remnant of his troop then fortify themselves, making a great fosse across the neck of land by which Ben Edar is joined to the mainland, and here they were besieged, with hard fighting by day and night, expecting that help should come to them from Ulster, whither they had sent messengers to tell of their distress.

Now Conall of the Victories was left behind to rule in Emania when Conor set forth to Leinster, and he now, on hearing how the King was beset, assembled a great host and marched down to Ben Edar.  Here he attacked the host of Leinster, and a great battle was fought, many being slain on both sides, and the King of Leinster, Mesgedra, lost his left hand in the fight.  In the end the men of Leinster were routed, and fled, and Mesgedra drove in his chariot past the City of the Hurdle Ford and Naas to the fords of Liffey at Clane.  Here there was a sacred oak tree where druid rites and worship were performed, and that oak tree was sanctuary, so that within its shadow, guarded by mighty spells, no man might be slain by his enemy.

Now Conall Cearnach had followed hard on the track of Mesgedra, and when he found him beneath the oak, he drove his chariot round and round the circuit of the sanctuary, bidding Mesgedra come forth and do battle with him, or be counted a dastard among the kings of Erinn.  But Mesgedra said, “Is it the fashion of the champions of Ulster to challenge one-armed men to battle?”

Then Conall let his charioteer bind one of his arms to his side, and again he taunted Mesgedra and bade him come forth.

Mesgedra then drew sword, and between him and Conall there was a fierce fight until the Liffey was reddened with their blood.  At last, by a chance blow of the sword of Mesgedra, the bonds of Conall’s left arm were severed.

“On thy head be it,” said Conall, “if thou release me again.”

Then he caused his arm to be bound up once more, and again they met, sword to sword, and again in the fury of the fight Mesgedra cut the thongs that bound Conall’s arm.  “The gods themselves have doomed thee,” shouted Conall then, and he rushed upon Mesgedra and in no long time he wounded him to death.

“Take my head,” said Mesgedra then, “and add my glory to thy glory, but be well assured this wrong shall yet be avenged by me upon Ulster,” and he died.

Then Conall cut off the head of Mesgedra and put it in his chariot, and took also the chariot of Mesgedra and fared northwards.  Ere long he met a chariot and fifty women accompanying it.  In it was Buan the Queen, wife of Mesgedra, returning from a visit to Meath.