Luca admits that she discovered she could transfer emotions, thoughts or memories through Dive Therapy and successfully brainwash or manipulate people. These thoughts scared her and she hid them deep inside her Cosmosphere. Despite discovering this ability, she never actually attempted to do it on a conscious level until you meet Witch Luca who attempts to take Croix's good qualities to complete herself.
A lot of the deeper Cosmospheres can be incredibly terrifying, especially since these levels revolve around the girl's darkest sides. The game does warn you how dangerous these levels are, and it isn't kidding!
Cloche's Level 6 Cosmosphere is probably one of the most disturbing and uncomfortable moments of the game. The main subject matter in here is Cloche's anxiety of not being the real Holy Maiden. The Cloche in this level is badly meek and afraid, suffering constant abuse from Luca. Even worse is that Cloche is unwilling to get away from Luca and sticking with her despite the horrific abuse due to her fear of and dependency on her. It's so bad that Cloche begs Croix to bring her back when he tries to take her away from Luca. The very worst part in this level has to be during the climax, where Luca forces Cloche to humiliate herself in front of all the people by admitting to being a fake and submit herself to Luca. This one level really show just how horrifying Cloche's view is in her insecurities. And the worst part? It's a level that isn't even supposed to exist and instead of ending in a Paradigm Shift, the whole level is obliterated requiring Croix to restart it in its true form.
Cloche's Level 7 Cosmosphere where it's a boiling mess of self-destruction and anger. Not only has Cloche gone over the deep end, but the world itself is like hell on Earth. Doesn't help how in this level, Cloche is actively trying to kill Croix and herself together.
Level 6 of Luca's Cosmosphere. In here, Luca is a witch who's considered by the denizens as the last hope to save the world from a dark abyss. However, it's also in here where it shows Luca's darkest side. She's very manipulative and deceitful attempting to trick Croix to hijack his mind and take his good qualities for herself. When Croix ends up hanging off a cliff after she pushes him, Witch Luca reveals to him how much she was deceiving him, giving him "The Reason You Suck" Speech before mockingly telling him that she loved him for how useful he was and how he was a fool for being so easily used. She even questions Croix what he even likes about her to begin with. While Croix is in shock from this, Witch Luca tries to kill him by throwing him off since he knows all her secrets.
Luca's Level 7: In this level, not only is she completely love-hungry and unstable, but she's also a dictator who so obsessive and vain about being loved by everyone that she'll have her followers kill anyone who goes against her by throwing them to the abyss. Even worse is these followers aren't doing it out of blind devotion, rather from fear of being killed. The climax is also pretty terrifying- especially in the Japanese dub- with Luca suffering from a massive breakdown after Croix rejects her shallow definition of love. The end result is the entire world collapsing.
Infelsphere Level 4. This is easily one of the most dire parts of the game. The girl of your choice completely changes to being very malicious and angry, where she then tortures the girl you didn't choose while ranting about her grievances and hatred towards her. The very worst part is that the heroine you pick isn't actually brainwashed by the Song of the level like you initially believe. At the end, it's revealed that she was doing these things consciously. This results in a massive fight between Luca and Cloche, with one nearly killing the other through shutting the Infelsphere. It's extra terrifying when listening to the Japanese Dub, since this part is voiced which shows how bad the tension between the two is.