Bak Full Moon Poya Day falls today (21st April).
This holy day celebrates the second visit of the Buddha to Sri Lanka, which took place in the fifth year of his supreme enlightenment in order to reconcile two local chiefs, Mahodara and Chulodara, uncle and nephew, who had fallen into disagreement and were threatening hostility over a throne beset with jewels. The theme of the day is Right Understanding (Samma Ditthi).
Naga Mahodara was then a King, gifted with miraculous power in a Naga Kingdom in the ocean. His younger sister had been given (in marriage) to the Naga-King on the Kannavaddhamana mountain; her son was Chulodara. His mother’s father had given to his mother a splendid throne of jewels, then the Naga had died and therefore this war of nephew with uncle was threatening and also the Nagas of the mountains were armed with miraculous power.
Mahavansa also records that the Buddha was accompanied by a deity to Sri Lanka. Buddha settled the dispute and the next development of events. Hovering there in mid-air above battlefield the Master, who drives away (spiritual) darkness, called forth dread darkness over the Nagas. Then comforting those who were distressed by terror he once again spread light abroad. When they saw the Blessed One they joyfully did reverence to the Master’s feet. Then preached the Vanquisher to them the doctrine that begets concord and both (Nagas) gladly gave up the throne to the Sage.