Shishupal or Sisupal (Sanskrit: शिशुपाल, IAST: Śiśupāl) was son of Damaghosh, king of Chedi, by Srutadev, aunt of Vasudev. Therefore he was not only cousin of Krishna, but also Krishna's implacable foe, because Krishna had carried off Rukmini, his intended wife. He was slain by Krishna at the great sacrifice of Yudhishthir in punishment of opprobrious abuse.
The Mahabharat states that Sisupal was born with three eyes and four arms. His parents were inclined to cast him out, but were warned by a voice not to do so, as his time had not come. It also foretold that his superfluous members should disappear when a certain person took the child into his lap, and that he would eventually die by the hands of that same person. Krishna placed the child on his knees and the extra eye and arms disappeared indicating Shishupal's death was destined at the hands of Krishna.
In the Mahabharat, Shishupal's mother was given a vow by Krishna, her nephew, that he would pardon his cousin Shishupal a hundred times per day and he will kill him when he exceeds the limit. When Yudishthir decided to make the Rajasuya Yajna. At that time Shishupal insulted Krishna as a cowherd and worthless to be honoured as a king. On an earlier instance he felt humiliated when Krishna rides away with Rukmini, his beautiful bride to be, and marries her. Shishupal who happens to be a great friend of Rukmini's brother Rukmi.
The Vishnu Puran contributes an additional legend about him. "Sisupal was in a former existence the unrighteous but valiant monarch of the Daityas, Hiranyakashipu, who was killed by the divine guardian of creation (in the Narasimha Avatar). He was next the ten-headed (sovereign Ravan), whose unequaled prowess, strength, and power were overcome by the lord of the three worlds (Ram). Having been killed by the deity in the form of Raghav (Ram), he had long enjoyed the reward of his virtues in exemption from an embodied state, but had now received birth once more as Sisupal, the son of Damaghosh, king of Chedi. In this character he renewed with great inveteracy than ever his hostile hatred towards Pundarikaksha (Vishnu), and by consequence was slain by him. But from the circumstance of his thoughts being constantly engrossed by the supreme being, Sisupal was united with him after death, for the lord bestows a heavenly and exalted station even upon those whom he slays in his displeasure."
His death forms the subject of the celebrated 8th century poem Shishupal Vadh.
- Dowson's Classical Dictionary of Hindu Mythology