Here is Moonsie, a secret boss for a small portion in the library. He is based on creepy bedtime stories and uses the blue soul on you, and fun enough Noelle fights with you in this battle. I feel like this would be fun and i hope you find it that way too

Meet the Lord's Exorcist, who is the secret secret boss of Ch3 in Chapterswitch, in which this is Exorcistinguisher having the power of the Lord's Hammer, trying to free Clover from his, "Unholiness", I can't wait for this to be possible, see ya soon >:)!

Meet Sheriff Buddy, yes you also get a Friend Inside Me boss, but instead of Friend Inside Me, it's Friend Corrupted Program, and Sheriff Buddy is actually a sweet guy when not a corrupted TV program, welp see ya and bye, enjoy these secret bosses >:)!!!!

Torawareta rivu~aiasan, the Leviathan within the depths of the Third Sanctuary. Imprisoned by an anchoring chain and put under spell to destroy everything in sight by the night, thanks to the Knight and their Shadow Crystal, a new type of enemy it seems..

Time to meet Eramb, you unlock under interesting circumstances, bye giving him the shadow mantle to free him from his stone form, but then he gets plugged ina nd is corrupted by Eram/The Mantle, and you and the party are sent into the game, welp see ya>:)

Time to meet Miss Florel, the Keeper of the Destroyed Garden. Yep you get want some of you want, a flower boss for ch3, and is basically a combination of flowey and muffet in terms of battle, personality, and design, hope you enjoy it bye >:)!!!!!!!!!!!!!

Meet the Lord's of Three: Guei+Titan Spawn as Cat Mike, Winglade+Wafer+Bilibiox as Small Mike and Organikk+Baalthizard as Cowboy Mike. It's actually Titan Spawn as Cat Mike, Winglade as Small Mike and Organikk as Cowboy Mike. Welp see you later, bye >:)!!

The Mantle Keeper, the Shadow Keeper, and the World Keeper, character, secret boss, and weird route boss for ch4. Yes Ralsei swaps with the old man, with provides and interesting and different storyline/arc for Noelle, well see ya soon and have fun >:)!!!

Seam, the High Mage, a castle town ch2 secret boss, testing you to see if you are worthy of even wielding the shadow mantle, in which of course after the fight he can't find, but he does have something, a shadow crystal in his empty eye, welp see ya >:)!!

Meet who swaps with Eram and the Shadow Mantle, and no the Sound of Justice does not swap with Eram, instead the Lord of the Hammer swaps with Eram and the Magic Axe swaps with the Shadow Mantle, but they are both heavily modified and changed, welp see ya