Onba is the main antagonist of Brave Story: New Traveler. She called out on False Travelers to help her destroy the Goddess and take her place.
According to Onba, she was all the negativity thrown away by the Goddess of Destiny when Vision was made. Because of this, Onda despised the Goddess. She plotted to replace her by calling out two False Travelers and help her destroy the Goddess.
At the gate to the Tower of Destiny, Onba disguise herself as Miki and tried to trick Tatsuya to give her the Demon's Bane, but failed. She explained her hatred for the Goddess. And told Tatsuya that she'll cure Miki if he help her destroy the Goddess. Yuno and the others convinced Tatsuya to not listen to Onba and that he can save Miki by defeating Onba. Tatsuya draws the Demon's Bane and pointed it at Onba. Onba asked why won't anyone side with her. Onba grew angry and fought Tatsuya and his friends. When Onba is defeated, she exclaimed that this was not the end and that she'll come back as long as they breathe.
After Onba disappeared, Miki was cured and all of Vision was save.
In her first form, Onba appeared as giant frog with a cloth on her back. In her second form, an upper body of a woman appears in the mouth of the frog. In this form, she has black long hair and has bleeding eyes.
In battle, she is seen to be chained.