
King Shalya was the ruler of the kingdom of Madra and brother of Madri (mother of Nakula and Sahadeva).
He was a skilled archer,formidable warrior and a powerful mace fighter. He was tricked by Duryodhana to fight the war on the side of the Kauravas.
While Lord Krishna was Arjuna's charioteer, Shalya was Duryodhana's charioteer. Through the 18-day battle, Shalya, who was the maternal uncle of Pandavas demoralised Duryodhana by constantly telling him that he was on the side of evil and would lose.
Shalya had a strange ability which made him invincible in battle. He would become even more powerful when more aggression was used by his enemies fighting against him
He was killed by Yudhishthira, because the eldest Pandava was not a man of aggression