Son of Ritayana, King of Madra, brother of Madri, the second wife of Pandu.
Duryodhana cut him off on the way to the Pandavas‘ camp and invited him to a feast. Salya thought he was with the Pandava forces.
When the mistake was found, Duryodhana blackmailed him to fight on the side of the Kauravas. Shalya asked to inform Yudhishthira and he would come back. Duryodhana agreed.
Yudhishthira now turned the tables and asked Shalya to become the charioteer of Karna (who fought on the side of the Kauravas) and to demoralize him.