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 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 >:)!!!!

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 >:)!!!!!!!!!!!!!

Here they are themselves, the ch3 shop character, Exorcitinguisher, Fire Extinguisher as Ramb, trust me it's for a fun reason. Yes he does actually have a shop UI, and has a connection to freedom and the secret boss like how Ramb does, so see ya soon >:)!

Welp, here is The Real Mike, yup mike is real and is a secret boss, and how you unlock him is basically similar to trying to find the eggman, but instead you do it after you beat the 3 mike stand-ins, so yeah you get Castle Town boss fights, see ya >:)!!!

I feel like it's time for you to meet the Preacher, the main boss of chapter 3, he is the Titan as Tenna. He believes that Clover has fallen off the path the holiness and puts him through the adventure in the Lord of the Hammer to bring him back, see ya!!

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 >:)!

Culti the Ritual Cat, a witch secret boss you can find in the second sanctuary, and in the lightworld they are Catti's occultism kit, and yes they will use the lightners in a ritual of some kind, but you gotta wait to see it so see ya and have a good time

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..

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 >:)!!!