Spy for Conchobar mac Nessa in most versions of the Deirdre story. Although the son of the king of Lochlainn, Gelbann was dispatched by Conchobar to see if Deirdre's beauty had faded while she was on the run with her lover Noíse. Noticing Gelbann peering through the window, Noíse threw a fidchell piece at him, putting out his eye. But Gelbann retorted that he would gladly surrender his other eye to gaze again upon Deirdre's beauty. In some versions of the story Conchobar's servant Tréndorn plays the spy.