And we had the horrible revelation that everyone in Death Libram (Idk about Margaret so she might throw this out the window) has received a power from Evelleon.

Grave's ring was created by Evelleon (It doesn't say her name but it's her voice talking)

She gives Milly enough power to become S-Class sinner

And I assume roughly the same for Parfait

Evelleon is definitely supposed to be the representation of this Libram. The rider of the Pale Horse.

It seems receiving power with her always costs something. A gambit with death?

Graves hasn't had a chance to pay her back yet. But she asks for her compensation regardless

Milly (nearly) pays with her life. In a way I wonder if she should have died? But maybe Evelleon just likes her enough not to?

And Parfait seems to be paying with her "value" as a powerful asset.

I'm not quite sure how the "illusions of joy" fit her the same way that idea applies to Graves, Milly and Parfait. But she likes the pursuit of happiness which is interesting.

I don't have a point I want to make exactly, but it does make a little nervous about Miss Margaret if the imagery of her we've seen wasn't already alarming enough.