Obtained: Speak to Eighter in the Lucca Village area a short distance away from Raditz’s crashed ship during the Rumble with Raditz main story mission
Objective: Defeat the rampaging robot
Follow the sub story marker to arrive in a ravine at the southern part of the map. Approach the group of robots there to trigger a fight. After the fight, a cutscene will trigger and the sub story will complete.