The Sudarshana Chakra (Sanskrit: सुदर्शन चक्र) is a pirouetting, disk-like super weapon with 108 serrated edges of Hindu God Vishnu. The Sudarshan Chakra is portrayed on right rear hand of the four hands of Vishnu
No atonement is necessary; it won't help the snakes now, after all. Rather, the only atonement required is gaining a lesson in the deaths of those snakes, and perhaps saving some, or some other animals, in the future.