Submission of Naga King Apalala, ca 2nd C.CE, Loriyan Tangai
A relief from Loriyan Tangai region of Pakistan at the Indian Museum Kolkata.
The legend: In the Swat river of the Gandhara Kingdom, there was a naga king called Apalala. He used to harass the local residents and they, in turn, offered him a tribute to stop harassing them. Once when the tributes started dwindling, Apalala was furious and turned himself into a Dragon. He threatened to invoke floods in the Swat river and annihilate the community. At that time Buddha with Vajrapani was visiting that area to propagate his thoughts. Vajrapani used the weapon Vajra (lightning) to bring down the mountain and subdue Apalala. Apalala submitted to Buddha and converted to Buddhism.
It was interesting to come across an article in Dawn (Pakistan) about the archaeological department invoking a slightly different version of this legend in the context of floods in the Swat valley. See story: https://www.dawn.com/news/563030
Stone stories 