A nāga king, converted by the Buddha.. He is mentioned together with āravāla, Dhanapāla and Pārileyyaka. The name appears in passages where the Buddha's powers are discussed (E.g., BuA.29). "Was not the Buddha honoured even by beasts such as āravāla, etc.?"
The story of the conversion of Apalāla does not, as far as I can discover, occur in the canonical books. In the Samantapāsādikā (iv.742) the story of the conversion of Apalāla (Apalāladamana) is given among the stories not included in the Three Councils (sangīti), but that it was known quite early in Ceylon is evidenced by the fact that, among the scenes from the Buddha's life represented in the relic-chamber of the Mahā-Thūpa, the conversion of Apalāla is mentioned (Mhv.xxx.84). The Divyāvadāna (pp.348, 385) makes reference to the story, and states that the nāga was converted shortly before the Buddha's death. Hiouen Thsang gives the story in detail (Beal: Records of the Western World i.122; also Legge: Fa Hien's Travels, p.29n.). During Kassapa Buddha's time, Apalāla had been a powerful man called Gangi. By means of his charms he subdued the dragons that attacked the country, and the people, in gratitude, agreed to give him tribute. Later some of them forgot their promise and he, in wrath, became a dragon after his death.
The Buddha Gotama visited him and preached to him. He was converted, but, for his sustenance, he was allowed to have one gathering of the crops every twelve years. It is for this reason that the White River (Subhavastu) overflows every twelfth year. The story is found in the Sūtrālankāra and other Mahāyāna books. See Nariman: Sanskrit Buddhism, pp.194, 274.
According to the Vinaya of the Mūlla-Sarvāstivādins, the Buddha converted Apalāla during a visit to Kashmir in the company of the Yaksa Vajrapānī (JA.1914, vol. iv.510).