Vasuki

Vasuki / वासुकी

Vasuki was a great King of the nagas and has a gem (Nagamani) on his head.
He was the son of Kashyap by his wife Kadru.
When Kadru asked her sons to assist her in deceiving Vinta so that she (Kadru) could win her bet, some of her sons refused.
Vasuki was one of them. Hence Kadru cursed them that they would burn to death in the serpent sacrifice of Janmejay.
Vasuki and his brothers tried to find a way to nullify the curse of their mother, when Elapatra said that he had overheard Brahma telling the other gods that the innocent serpents would be saved by Astik, son of Vasuki's sister Jaratkaru by the sage Jaratkaru.
Vasuki personally looked after the welfare of his sister and when the sage Jaratkaru came looking for a wife having the same name as his, Vasuki gave him his sister's hand in marriage.
When Janmejay performed his serpent sacrifice, Takshak, Vasuki, etc. would have been killed in it, if Vasuki had not sent his nephew Astik to stop the sacrifice.
Vasuki served as the churning rope during the Samudramanthan.
Shiv made Vasuki his bow-string during the burning of Tripur.
Bhogvati, a city in Patal, the lower most region, is where Vasuki reigns.
Shatshirsha was the wife of Vasuki and Chakra and Dhritrashtra were their sons.