Ravana appears in the Ramayana as the demon-king of Lanka and the principal antagonist of Rama. In character, Ravana is born to a Brahmin father, and grew up to become a great scholar. He performed a penance that took many years, pleasing the creator-god Brahma, who granted him a boon. Initially asking for immortality, but was refused, Ravana asked for protection against daevas, demons and spirits. He later went on to become king of Lanka, and soon king of all living things. His hubris led him to kidnap Sita, Rama's wife. In retaliation, Rama incarnated as a human, circumventing the boon given to Ravana, and killed Ravana.
"Origin: Sri Lanka. The king of the Rakshasas. He has ten heads and twenty arms, copper eyes, and a body that can reach the clouds. After intense penance, he attained invulnerability from gods and demons. However, he was defeated by Rama, and avatar of Vishnu."
—Shin Megami Tensei A-Mode DDS Dictionary
Ravana cannot be fused until after he is either defeated (Law and Neutral) or joins the player's party (Chaos).
Ravana is the demonic form of Varin Omega, empowered through the "Turbulence" Atma. It is fought in Ajna, in two forms. First, he appears as a chameleon-like creature, capable of turning invisible. Due to this, it appears in a line of six possible attack targets. Any multiple-target attacks will be nullified: it has to be hit in the exact attack target to receive damage.
After enough damage has been dealt, Ravana will open its tail and encase itself in a protective shell. It will no longer be able to turn itself invisible, but it will gain its signature move, "Hunger Wave". This attack is capable of inflicting the "Hunger" status effect, which causes the affected party members to either lose HP or attack one of their own, and can only be cured once per turn. It also has a strong Wind-type attack, Infinite Wind.