Shakuni was the son of Gaandhaara king. He was brother of Dhritharaashtra's wife Gaandhaari. Thus he was maternal uncle to the kouravas and was biased in their favour. However, he spoke the right way to Duryodhana on one or two occasions.
After his sister's marriage with Dhritharaashtra, Shakuni lived with them for many years. It was he who encouraged Duryodhana for the tricky dice game to win paandavas' kingdom. In fact, he actually played the game in person as Duryodhana's proxy. He was said to have some mysterious power of winning every stake in the game. Thus he won for duryodhana, Yudhishthira's wealth, kingdom, brothers and finally encouraged Yudhishthira to stake Droupadi too. He was considered one of the bad quartet viz., Duryodhana, Dushshaasana,Karna and Shakuni.
He was with Duryodhana when they seized king Viraata's cows on the northern side. He and his son Ulooka stood naturally on the kouravas side in the war. Both were killed by Sahadeva on the eighteenth day.
Even now, a wicked man and a bad counsel is deridingly referred to as Shakuni.
"After praying to Naaraayana, Nara, Sarasvathi and Vyaasa, then one should recite the Jayam."
DEDICATED TO MY DEAR NIECE VYSHNAVI KRISHNA