The infant Ken Arok was placed in the Brantas by his parents who hoped he would be found by a wealthier family and get a better life.
His foster father taught him all his criminal skills and young Ken Arok grew to be the most cunning thief in Kediri.
His effort was successful and later he managed to get Ken Arok to become an attendant of Tunggul Ametung, a powerful regional leader of the Tumapel area.
Legend says when the wind blew over her dress and revealed her legs, Ken Arok said that he saw a beautiful light shining.
He later told this to his teacher, who stated that it was a sign that Ken Dedes would bear a royal dynasty and any man that took her as wife would be a King.
Ken Arok, already infatuated by her beauty, became even more eager to take her by any means —including killing Tunggul Ametung if necessary.
Thus, Ken Arok needed an exceptionally strong weapon to defeat him and also had to find a way to do so without himself being punished for the crime.
However, Mpu Gandring stated that he still needed several months to perform rituals to imbue the kris with more magical power, not only to make it strong but also to prevent it from becoming an evil weapon.
He gave the kris to Kebo Ijo, another attendant of Tunggul Ametung, a greedy man known to be fond of collecting krises.
Before Kebo Ijo was able to defend himself, Ken Arok stabbed him to death, on the pretext of avenging Tunggul Ametung.
[citation needed] The kings of Majapahit were believed to be descended from Ken Arok, as also were the Mataram rulers.
[citation needed] The story of Ken Arok has been enduringly popular in Central and East Java.