Your accompanying picture is of Greek mythology, not Hindu Auras. It's Adolf Hiremy-Hirschl's "Souls on the Banks of the Acheron" (1898). Hermes, with his winged hat and caduceus, stands at the edge of the River of the Dead (Acheron), facing a crowd of recently deceased souls who implore him to save them from their trip to Hades. But it's still a very powerful and evocative image of despair. Thanks for posting it.
In Hindu and Buddhist cosmology the Asuras are enemies of the Devas, although some can be allies of them, and as heroes to mankind. There are hundreds of them (not just four), and they used to live with the Devas in heaven, although they were always arguing with them. However, at a celebration in Heaven, all the Asuras got drunk and the Devas used this opportunity to literally push them out of the sky, and the Asuras fell into the world below. The Asuras are continually fighting with the Devas to get back into heaven, and because of this struggle to get back 'on top' they are seen as hyper-competitive and paranoid. They are driven by a desire to beat everyone at being better, having the most, and being powerful. They therefore resemble the material side/negative emotions of man - anger, war, pride, ignorance, arrogance, greed, etc. They might accomplish good things with these powers (and so be beneficial to man and gods), but ultimately they are self serving.
I'm not familiar with the names you give as being Hindu. Anshar is a Mesopotamian sky god, Taranis is a Celtic god of thunder, and Thiasus is the drunken retinue of Dionysus.