First thing first. I am dumb. When discussing Diablo IV before, I didn't list my ideas for a potential sequel. I didn't give you my entire thought process. Apparently this was a mistake, because some of my initial ideas might turn out to be correct, and now I don't have any credible way to prove it.
See, at first I wanted to go forward. My very first idea was another expansion for Diablo III with Trag'Oul as the end boss. A huge cosmic dragon is the only one strong enough to fight the Nephalem and pose a challenge. And as the Guardian of the balance he might think that the Nephalem has too much power in his own hands. We are an inbalance.
When it became apparent that Diablo III is beyond saving, I wanted to look for a way to depower the Nephalem. Makes sense really. We need to start the game as level 1. So either we lose all our powers, or we lose powers and die and a new hero takes our place. Now the Nephalem were depowered by the World Stone. So it makes sense to try to undo the destruction of the World Stone. Send somebody back in time to make sure it remains intact.
And this is where Lilith comes in. She is an interesting figure. IRL she is infamous as Adam's first wife. One, who considered herself equal, and wasn't willing to just stay at the bottom. Sounds pretty good actually. Call me a pervert, but I prefer my women with some personality. Doormats don't turn me on. Problem is, none of this is in the Bible. This was written un a satirical text much much later. The original Bible contains the word lilith only once. And it is in a list of uncleen creatures. Lilith is a demon. Translations disagree if she is an air demon or a night demon, but she is more or less vampiric. These types of female demons go back all the way to the epic of Gilgamesh. Things only got more complicated later. One text claims that there are two Liliths. Matron Lilith is the wife of a demon and they have a daughter named Lilith. This second one is actually the serpent who tempts Eve. This could still be Adam's ex being sligtly yandere, but who knows? Kabbalah by the way lists her as a seductive demon who can turn into a butterfly.
Lilith is a popular figure in fiction. Secret World, Trinity Blood, Vampire the Masquerade...and of course Diablo. Our version is the daughter of Mephisto, the Lord of Hatred, and an unknown mother. Funnily enough her original lore listed her as the mother of Andariel, but this was retconned when the Three Prime and four Lesser evils were established as the seven heads of the evil Tathamet. While so far only appearing in the non-canon Pandemonium event of Diablo II, she is an important part of the backstory. It was she and the angel Inarius who created the world of Sanctuary, and even humanity itself.
At present Lilith is inside the void where she has been banished at the end of the Sin War. Supposedly there is no way out, but it is possible that when Malthael sucked all souls into the Black Soulstone, he unknowingly sucked Lilith out of her prison. If this indeed happened, Lilith became free once more, when the stone was shattered. Freedom would enable her to plot the downfall of the Nephalem, and pretty much everyone else.
So what does it have to do with Diablo IV? I'm glad you asked. An alleged page of the Art of Diablo book, was leaked. It features a page about Lilith which talks about her debut in Diablo IV. Whoops. Granted even if I can't prove this was my idea before, I can still be excited for BlizzCon. These better not turn out to be fake, because this sounds like a dream come true, so far.