Devas (AKA Daevas, Dēwān/Dēw-hā, Theǒí, Diī, Ases/Æsir/Tues/Tívar, Dievaĩ) are beings from Indo-European myth. In most religions including Italic, Asian, and Indo-Dharmic religions, they are holy, but in Perso-Irano-Magian lore they are demonic.
In Hinduism, Devas are celestial beings associated with various aspects of the cosmos. Devas such as Brahma, Vishnu, and Shiva form the Hindu trinity known as the Trimurthi and preside over the functioning of the cosmos and the evolution of creation.
In ancient Persian mythology, prior to the rise of Zoroastrianism between c. 1500-1000 BCE, the supreme god was Ahura Mazda (“Lord of Wisdom”), champion of order, against the dark forces of Angra Mainyu (“Destructive Spirit”) and his legions of chaos. The spirit of discord, Angra Mainyu (also known as Ahriman) led the legions of dark spirits known as the daevas. His sole purpose was to disrupt the order established by Ahura Mazda.
In Sri Lankan mythology, the Deva are a mythical people who lived among the Naga, Yakkha and Raskha. They ousted their arch enemies the Raskha from Sri Lanka, with the help of Vishnu. They were then subsequently conquered by King Ravana of the Raskha. According to the Mahavamsa and Ramayana, Gautama Buddha met the Deva at Mahiyangana and converted them to Buddhism. Sumana Saman was a leader of the Deva who came from the central hills of Sri Lanka and is worshipped as a deity by some Sri Lankan Buddhists. He is said to be the guardian of Samanalakanda.