I present to you all, my (possibly) superthread On how and why the Unknown God from Genshin Impact, and The Herrscher of Void/God Kiana/Sirin from Honkai Impact!

First off! We’ll start with the obvious things that constitute a possible connection.

They share the same Japanese Voice actress! Rie Kugimiya.
Usually this is a stretch reason, but considering everything else, it’s not unlikely that it’s the same character.

Secondly, their Appearances.
The both have very long white hair with identical bang style, and a very noticeable small piece of hair on top that curls upwards. That’s a defining part Of all of Kiana’s hairstyles, and for it to be shared with this god says something.

Another notable thing is their eyes. They both have Glowing golden eyes with very similar appearances. They contain a ring, and a 4-point star pupil. Resemblant of a scope if you will. That’s The Herrscher of Void’s defining characteristic

If you’d even like to take a look at their outfits, there’s resemblances including the black fur collar, the designs on the torso and chest, and the use of something similar to coat tails/skirt. The Herrscher can change their outfit and they aren’t stuck with one. Sirin does this