Obtained: Speak to the Alien Male and Alien Female tourists during Gohan’s Latent Power main story
Objective: Look for the Maristone
Follow the marker north through some mountains to reach the northern part of the island bringing you to a search area. The Maristone is located under a giant rock near the center of the search area. Use your Ki Blast to destroy the rocks then collect the Maristone and return to the tourists. As you approach them, a cutscene will trigger leading to a battle with three members of the Frieza Force. Defeat them to complete the sub story.