Asuras are entities that take on varying roles in the Asian religions.
In the old Vedic religion, they were simply gods of moral/social phenomenon who regularly competed with the Devas, who were gods of natural phenomenon.
In Hinduism, they are fanatical, demon-like entities associated with carnal and materialistic pleasures, and often thirsted for violence, opposed to the more peace-inclined Devas. There are many kings and rulers of the Asura, but the Megami Tensei series' Asura Lord is based on Virocana, the king of the asuras who, alongside Indra, searched for the secret of enlightenment.
In Buddhism, they are the lowest rank of deities and are jealous gods addicted to various malign passions, while said to be one of the four unhappy births, being representative of a human being incapable of peace and always angered with the world, while also seeking strife and violence. In Japanese Buddhism, they are demigods, or semi-blessed beings. Powerful protectors of Buddhism, yet fierce and quarrelsome, they are partly good and partly evil, like humans. Their realm is believed to be a world of strife said to be located on the ocean floor. Some say Ashura was an Indian royal who converted to Buddhism. In other traditions, Ashura was a sun goddess who was feared for bringing droughts. The leaders of the Asuras were called Asurinda or Asurendra ("Asura Lord"). The principal leaders are Vemacritin (also called Vepacitti), Rahu (also called Veroca, Verocana, or Virocana), and Paharada. The appearance of the Megami Tensei series' Asura is most likely based on the Japanese Buddhist depiction of the Asuras.
However, in Zoroastrianism, Asura is known as Ahura, and are depicted as the forces of good, led by Ahura Mazda. In fact, the Indo-Iranians, the term asura (or in this case ahura) originally referred to divine beings on par with the gods. After the Aryans went their separate ways from the Iranians, the asuras came to be seen as rival gods, eventually even demonic. The struggle between the devas and the asuras possibly reflects the conflict between the tribes who worshiped a pantheon led by the god Indra and the tribes who worshipped the gods called the asuras.
Near the end of the final dungeon, the hero and his party encounter Asura. If the hero recruited Lucifer, Asura is turned back into Ahura Mazda, his true form and joins the party. Otherwise, he will fight the hero.
As the one responsible in leading the forces of the Gaian Church in order to intervene in God's summoning on the Great Cathedral and bringing forth a world of freedom under the demons (and, for some, a world of survival of the fittest), Asura stands in his chambers located on the heart of the last floor basement of the Messian cathedral as the last enemy and final boss fight the protagonist must face on Law and Neutral alignments; while serving as a non-playable ally if he is Chaos aligned, providing aid in the attainment of the "Devil Ring"--a valuable item needed for the final showdown against Michael to become available. In contrast to this, Asura's own throne room is inaccessible unless the player have the "Angel Ring" in his possession, but only if he follows the Law route. No item is required in the Neutral path.
He poses as the leader of the Gaian army that have taken control of the inferior part of the Cathedral, and serves as the most powerful servant of Lucifer on Earth, guiding his demon generals on the complete obliteration of the Messian faction alongside the Chaos Hero and his female partner Rie.
After encountering the hero, Asura mocks him. Stating that "to have betrayed one who cared about [him] (referring to the Chaos Hero) in order to follow the orders of one who has done nothing for [him]", he is truly a "shining example of a servant of God". With that said, Asura proceeds to engage the heroes in the final battle, where he is slain and the balance of the world finally restored.
It is interesting to note that, according to him, he is actually Ahura Mazda, cursed by God to be the demon Asura.
"A violent group of demons in Hindu lore. They were very powerful and caused the gods great trouble. They are a strict group and attack anyone who runs counter to their ideals. They were originally gods of light who were worshipped in Persia. The Zoroastrian god Ahura Mazda was one of them."
—Shin Megami Tensei: Strange Journey Compendium
Asura appears as the violent demon lord of Sector Delphinus, initially as a mass of Formless demons scattered through Delphinus. These could possess crew members and manifest a form of violent insanity until Zelenin and the Protagonist intervened using special energy guns to drive the demons away. The fleeting demons began coalescing in giant hives around Delphinus' higher levels. When a sizable number of them had been destroyed, they gathered in a giant stone statue of Asura, recreating their massive form.
Asura is a violent demon who seeks to "polish" the human spirit by having it devolve into a state of savage barbarism. Fittingly, his signature attack is Asura Roga, an attack that leads the targets to develop the Rage ailment, which causes them to mindlessly attack any target in the battlefield: themselves, the enemy, or their own allies. After being destroyed, he leaves behind his rare forma and Delphinus' Rosetta.
Asura later returns in Sector Fornax, in which he appears as an invisible demon which can hurt the Protagonist with impunity unless he has the upgraded Enemy Search program. Upon being discovered, he manifests a Formless demon to attack while he hurries to Fornax' basements to shed his shape and assume his true form - Asherah.
Asura is the highest level Sun ArcanaPersona that can be summoned. It is only available after completing either the Ayane Matsunaga Social Link and receiving the Handmade Ticket from her or completing the Yumi Ozawa Social Link and receiving the Annotated Script depending on whether you chose the Drama Club or Music club for your cultural activity.
Devil Summoner: Raidou Kuzunoha Vs King AbaddonEdit
Asura appears as an optional boss in Raidou Kuzunoha Vs King Abaddon. Provided that the player has completed all other quests by the Yatagarasu and provided that Raidou's alignment is Lawful, the case file "A critical request" shall open up for the player in Chapter 7.
The player must go through the Akarana Corridor to find Asura. Asura will explain that he wishes to leave to go to an alternate space-time where the forces of Chaos have waged war upon God. He explains that his current form as Dainichi Nyorai is not his true form and that he is Ahura Mazda. Raidou must choose if he dares to challenge Asura and then after the fight he must decide Asura's fate. As the player, you can choose to allow Asura to go join the armies of Chaos so that he may pursue his desire in once again becoming Ahura Mazda or to have him return to being Dainichi Nyorai.
Gouto will comment about the potential ramifications Raidou's decision could have on their world.
Asura does not actually appear in both games, but as a demon title given to the demons initially "tuned" in the virtual battlefield, Junkyard, because the digital world is constructed under the "Asura Project" for selecting battle AI. In the second game, another group of demons which initially tuned in the "real world" is classified as "Yaksa" in contrast to the Asura demons. Even though many demons exit the Junkyard to the "upper realms", they still retain the Asura title during boss battles, such as Agni and Hayagriva.
"A violent group of demons in Hindu lore. They are very powerful and caused the gods much grief. They are a strict group who attacks anyone that runs counter to their ideals. They were originally gods of light who were worshipped in Persia. The Zoroastrian god Ahura Mazda was one of them."
—Devil Survivor 2 Compendium
Asura is unlocked by reaching Fate rank 3 with the Anguished One. It is also the strongest member of the Deity race.