Devas and Asuras are the two great families of beings that structure much of Vedic and Puranic cosmology — the Devas (“shining ones”) ranged against the Asuras (“power holders,” later cast as anti-gods), locked in a rivalry that runs through the Vedas, the Puranas, and stories like the churning of the cosmic ocean, Samudra Manthan. Both groups, in most tellings, descend from the same father, the sage Kashyapa, through different mothers, Aditi and Diti — a detail that already signals this is less a war between good and evil species than a contest between two tendencies born from a shared source.
The Bhagavad Gita gives the clearest philosophical version of the distinction, in its sixteenth chapter, contrasting daivi sampad — divine qualities such as fearlessness, purity, generosity, self-control, and truthfulness — with asuri sampad — demonic qualities such as arrogance, harshness, and a hunger to acquire and dominate without regard for others. Devas, in this reading, act to sustain the wider order (rita or dharma) even at cost to themselves; Asuras act to expand their own power and possession, treating the world as something to be seized rather than shared.
What keeps this framework from collapsing into simple mythology is that Vedanta and yoga read Devas and Asuras primarily as psychological forces, present in every person rather than sealed off in two separate races. The Gita explicitly asks the practitioner to examine which sampad currently governs their own choices. Practices such as the churning of the ocean become allegories for this inner labor: Devas and Asuras cooperate, however unwillingly, to churn the ocean of the mind, and only sustained effort — using even the resistance of one’s own contracted, asuric tendencies as leverage — brings up the nectar of a settled, generous awareness.