how big of a powercreep they will be?

Nibelung created the Moon sisters and divided among them the power they needed to substitute Nibelung while he was away. Phanes enslaved them to his will with the same crowns he used to enslave the seelies, or the halos and with their help took over the Authority of Reason and with it Teyvat's rules. The sisters became 3 of the shades and the fourth is unknown.
Of the shades the most obvious former moon sisters are Ronova and Istaroth, corresponding to The Crimson Moon (Formerly The Iridescent Moon) and The Eternal Moon respectively. It is also possible that Iridescent once held authority over both life and death, meaning all four shade authorities came from the moons.

>>530660409
no but she is a dork that the other shades make fun of behind her back, including Asmoday

>>530639250
They're the primordial one's vtuber group.

>>530601081
>God
>Crimes
Female anon...