A mission to Telos IV was undertaken by Jedi Masters Qui-Gon Jinn and Tahl, Jinn's apprentice Xanatos, and the Masterless Padawan Orykan Tamarik in 53 BBY.
For some time, many members of the Jedi Council, including Grand Master Yoda, had expressed their concerns about Qui-Gon Jinn's apprentice Xanatos, and decided to give him one final test before granting him the title of Jedi Knight. Xanatos and Jinn were joined by two other Jedi, Tahl and Orykan Tamarik, to undertake a mission to the planet Telos IV.
Jinn pushes Crion into the fire.
When the Jedi arrived, they found out that Xanatos's father, Crion, had become a tyrant of the planet, abusing his power as governor. After the death of his sister Nason, Xanatos was tempted by his father's power and wealth and joined him to rule the planet. This lead the planet to a civil war.
Crion was confronted by Jinn, who accidentally killed the governor to save Tamarik. Witnessing his father's death, Xanatos became enraged and took a ring from Crion's finger, searing hot from the fire he fell in. He branded it into his cheek, creating a broken-circle scar. Swearing his revenge, Xanatos fled.
Jinn returned to the Jedi Temple and blamed himself for Xanatos's failure, renouncing his success in training his first Padawan.