Or only his retelling?

Even if something is "off", I don't think he's evil, or even insane. Just very misguided as to what "goodness" in Randland is.

Gaunt face set with grim purpose, Byar galloped with the sinking sun behind him and never looked back. He had seen all he needed to, all he could with that accursed fog. The legion was dead, Lord Captain Geofram Bornhald was dead, and there was only one explanation for that; Darkfriends had betrayed them, Darkfriends like that Perrin of the Two Rivers. That word he had to carry to Dain Bornhald, the Lord Captain’s son, with the Children of the Light watching Tar Valon. But he had worse to tell, and to none less than Pedron Niall himself. He had to tell what he had seen in the sky above Falme. He flogged his horse with his reins and never looked back.