In Hinduism, the Asuras are a group of power-seeking deities related to the more benevolent Devas (also known as Suras). They are sometimes considered nature spirits. They battle constantly with the Devas.
In early Vedic texts, both Suras and Asuras were deities who constantly competed with each other, some bearing both designations at the same time.
Later, in the Puranas, Kashyapa is portrayed as the father of both, Devas and Asuras. In the Puranas, Kashyapa is said to have married 13 daughters of Prajapati and fathered all beings on earth including Devas, Asuras, Manavas (humans) and the entire animal world.
Hinduism has many stories of Asuras and Devas fighting each other. Mostly they fight about who will get the best prayers from the worshipers.
In Hinduism the Asuras are said to be beings of moral and social things. Like truth and marriage. The Devas are said to be beings of natural things. Like the sun and the rain. In Hinduism, the Asuras are said to be “older”. And the Devas are said to be “younger”. There are very many Asuras and Devas. Two hundred years ago someone counted them and said there were over 2,000 Devas and Asuras. So naturally not all Asuras are very important. But some names have been forgotten since then, and others have been added. This is why Hinduism is called a “living religion.” It is changing all the time.
In order to explain the demonization of Asuras, mythology was created to show that though the Asuras were originally just, good, virtuous, their nature had gradually changed. The Asuras (anti-gods) were depicted to have become proud, vain, to have stopped performing sacrifices, to violate sacred laws, not visit holy places, not cleanse themselves from sin, to be envious of Devas, torturous of living beings, creating confusion in everything and to challenge the Devas.
It is significant that it was not for their sins that the Asuras had to be destroyed but because of their power, their virtue, their knowledge, which threatened that of the Devas—that is, the gods of the Aryas. Once defeated, they serve the gods faithfully.