Barong and Rangda already known in pre-Hindu. Barong is a symbol of goodness while rangda is a symbol of wickedness. The realization of the Barong form is a quadruped resembling a lion and Rangda is a scary form with spiky fangs in her mouth.
This legend begins from the curse that given to beautiful queen named Ratih. The reason why Ratih is cursed because Ratih has many vices. So she was cursed to be a very frightening creature with two spiky fang in her mouth, long hair dangling to the ground, big eyes and stared, also long nails in every fingers.
To bring back the original form (beautiful queen), she had to kill Sahadewa (son of Goddess Kunti). When doing this, Ratih accompanied by one of her students named Kalika. But in the end, Ratih was failed and apologize to Sahadewa, her apology was accepted by Sahadewa. After knowing that Ratih was defeated, her student Kalika wants to avenge the defeat. With confidence Kalika comes to Sahadewa, because he think he was already stronger than before.
In this fight, several time Kalika change his form. First, he turns into a very great boar, but it can defeated by Sahadewa. With his remaining strength, Kalika transform again become a big crow. It was useless, Sahadewa still unbeaten. Finally, Kalika can not take it anymore and use his full power. He changed into Rangda form. Because of its strength, Sahadewa become compilated to beat it. For winning the figth, Sahadewa transform into Barong. They continue to fight relentlessly. But, their strength are balance, then nothing is lost or won. So this became an eternal fight.
This legend has taught us that the good things against the bad things is the eternal struggle in every human life.