In this event, clearing event stages gets you keys to fight the boss. The boss drops masks for the box gacha, where Christine Junna Hoshimi is the main reward. Story chapters will be unlocked based on the amount of boss kills, regardless of difficulty.
Make sure to equip the event memoirs. They will allow you to deal much more damage to the boss.
The boss for this event is Space type. A good tank will be helpful, and any offensive Moon type units will be able to deal good damage.
From /u/starlight-gatherer: Only do the 4★ if it can be cleared in 2 attempts!
In particular, Black Lion Kaoruko is recommended to stun the boss to avoid some extra dmg being dealt to you!
Event characters and memoirs should be prioritized. They will give you a large boost when fighting the boss.
Using Seisho girls will give you a large boost, as they are the only type to deal +10% damage for this event.
Note: The 4★ Phantom Nana Daiba is not a limited character and will be added to the normal gacha pool once the event is added.
|4★ Phantom Nana Daiba||+200% Damage against Boss|
|3★ Christine Junna Hoshimi||+100% Damage against Boss|
|4★ Phantom and Christine Memoir||+50% Damage against Boss, +80% Damage if Max Uncap and Max Level|
|3★ The Opera House Expert Memoir||+30% Damage against Boss, +60% Damage if Max Uncap and Max Level|
|3★ Trying Out The Mask Memoir||+30% Damage against Boss, +60% Damage if Max Uncap and Max Level|
|ALL Seisho Music Academy Stage Girls||+10% Damage against Boss|
Boss Difficulty Levels
|Difficulty||Keys Required||Mask Drops|
Credit to /u/shocktopramen for the mask numbers for the 3★ and 4★ boss!