Ghost Mystery is a time-limited event that becomes available at experience level 11 and has 7 stages.
Each stage has its own objectives for collecting Precious Objects and corresponding rewards.
You can reveal Precious Objects using pickaxes obtained by completing levels or locations.
Collect all the objects on the field to claim the stage completion reward and unlock the next stage.
You can earn additional pickaxes by completing levels and locations with an active anomaly or a high rank.
Once you have completed all stages and received all rewards, the event ends.