Sires del Cor
Presented as the King of Ireland and Norois in the Second Continuation of Chrétien’s Perceval. He ruled the Castle of the Horn in the Land of the Horn.
The ‘horn’ to which his name refers hung outside his castle. Perceval blew it and summoned the Lord to battle. After defeating him in combat, Perceval sent the Lord of the Horn to Arthur’s court as a prisoner.
Source
Second Continuation of Chrétien’s Perceval | Attributed to Wauchier of Denain, c. 1200