I recently finished Dead Estate (steam version) and by finished I mean I got all the medals. No need for such a loud applause, yes, I am cool. (sarcasm signpost)

Anyways, I had this suden thought about Roselia Valentine (Cordelia's mom).

According to notes in Assignment Anya, this is the second time Leviathan tries to devour Earth. First time he was defeated by unknown sorceress.

Now, let's summarize what we know about Roselia Valentine. 

1. She can fly the broom and create portals (as seen in Cordelia's normal and true endings)

2. She can cook all kinds of magic stuff including ambrosia that heals everything and cookies that are better than bullets.

3. She is the only one who is not bothered at all by all the stuff happening in the mansion.

So, combining all this. I came up with a headcanon that Roselia is actually the one who defeated Leviathan previously, she is actually the strongest character and could easily wipe the kitchen floor with Cybil and her cult. But she is like "No,no, I'm on retirement and my daughter needs personal growth anyway, so let the young ones do the heavy lifting, I have my kitchen to take care of".

Also, I just finished gathering all the medals. Feeling really proud of myself.