Once one of the Eight Guardian Generals that led the Shinkoku Army, he was betrayed by his fellow Generals, who abducted his daughter, killed his wife, framed him for the murder of the Emperor, and left him for dead. Even in death, though, he was filled with an uncontrollable rage that led him back to the world of the living. With the help of a golden spider...
Asura has been shown to take numerous forms, usually depending on his level of wrath. His standard form is as pictured above, although while in combat situations he is usually in his Vajra Asura form, which is similar except his entire arms are metallic instead of simply his forearms. When particularly enraged he can increase his number of arms to six in a form known as, appropriately, Six-Armed Vajra Asura. This form is to be feared, toppling Seven Deities member Wyzen even after Wyzen grew to a planet-dwarfing size and attempting to crush Asura with his finger.
Asura's most demonic form is known as Wrath Asura. This is when he has lost all control of his wrath, turning into a devilish beast who sees no logic and will not listen to reason. He becomes extremely powerful, pummelling and killing Sergei of the Seven Deities before nearly doing the same to his brother-in-law Yasha until Yasha was able to break him out of the form. When in this state Asura's arms take the form of enormous limbs floating behind him. The form is harmful to Asura himself and is extremely unstable due to the amount of Mantra it requires. Attempting to use it to rescue Mithra from the Chakravartin nearly resulted in his death. Asura is usually black or molton red/orange/yellow in this state, pretty much unrecognisable to his regular appearance.
Mantra Asura is the form used to defeat the mighty Gohma Vlitra. In this state Asura was provided with copious amounts of Mantra by his daughter Mithra, increasing the size of his arms, his overall power and his armour. He flew into the heart of the creature and, alongside Yasha, destroyed the beast within.
Asura the Destructor is Asura's final form and by far his biggest. After being fitted with the Mantra Reactor by Yasha this enabled Asura to absorb any amount of energy without the risk of death. When the Chakravartin attempted to wipe out Gaia with an energy beam Asura stood in front of it and took the blow himself. This extraordinary amount of energy turned him into Asura the Destructor, a being even bigger than Gaia itself. In this form Asura becomes metallic grey with six arms and he is incredibly strong, destroying numerous stars and planets thrown at him (quite literally) by the Chakravartin en route to destroying him once and for all.
In contrast to these strong forms, Asura has occasionally had to fight with no arms after losing them in one way or another. This is probably his weakest form. Despite this, following his defeat of Augus that left him armless he managed to defeat incoming gohma by carrying a fragment of the Wailing Dark sword in between his teeth.