I mean, honestly I'm quiet shocked that we didn't really see her in this game. Sure sure there is a head in the treasury that looks like hers...but that kinda makes no sense for how she really ends up and is probably just an Easter egg. For the type of game this is, I kinda expected to see like a pregnant Rabianne attached to an eldritch slug god pumping out babies and Lilia must put her out of her misery finally. Then again, I still expect something to that effect to happen maybe in a DLC. Like if my theory is correct and Lilia is trapped on the otherside at the ending, with the slug, and the DLC continues that, where you have to just endlessly fight in the otherwold till your strength gives out and become the plaything of a whole dimension of eldritch gods. Maybe you'll be able to find the actual Rabianne there trapped like you. Either find her in a state where she is fully corrupted and is a mother of monsters (which is very in line with the themes) or perhaps if the game wants to take a hopeful turn just once (I find it unlikely), maybe you can find her also still fighting the evil gods and the 2 of them can team up to actually escape or even put an end to the threat for good (and then if you game over you can still have the scene of both of them becoming eldritch mothers trapped on the other side forever).