The shadow mantle quest has to be one one of my favorite things from the new chapters.

The whole thing is basically just creepypasta, and it has all the old tropes of what you'd expect, like how the game feels haunted, it's self aware and how you're doing things you're not supposed to do. But those ideas are executed so well it genuinely feels like it's an actually good creepypasta and not one that tries too hard.
It helps how it's happening in the dark world, so all the weird shit happening doesn't feel like out of place

The most unsettling part is killing the monsters that resembles Undertale characters, which make you think if killing them would ruin your pacifist run. And I do love you how finally get access to the bunker after years of speculations, even if it's in a video game format and not the real thing. Kris' reaction of trying to keep you way is also interesting.

Oh and gotta love when mini Kris jumps from the screen, and it's revealed how you put your literal soul in the game.

I hope Toby does something like that more in later chapters. He does creepypasta horror very well in his games