So, there is this old MMO out there called Anarchy Online. It was one of the first large third person 3D MMOs, first launched in 2001.
The game is still running, it has a small, but loyal player base.
https://en.wikipedia.org/wiki/Anarchy_Online
Anarchy Online's 2nd and largest expansion launched in 2003. It introduced several large new zones and tons of content.
It's title....
Shadowlands.
The Shadowlands was a parallel dimension connected to our own, its different areas were thematically inspired in different areas of the "afterlife", the zones ranging from the paradise like Nascence, moving onto Elysium, Scheol, Adonis, Penumbra, Inferno and finally onto Pandemonium.
The Shadowlands are populated by various factions that you end up aligning yourself with, these include the angelic Redeemed, the demonic Unredeemed and the neutral Guardians all whom oppose the forces of The Beast, an incarnation of entropy itself which is slowly consuming the Shadowlands and gradually reaching into our reality (the game is set in a scifi future on a different planet).
As someone who played Anarchy Online, everything I see from Blizz on their Shadowlands feels...oddly familiar.
I'm not saying it's an outright copycat, but I really do think they might have taken..."inspiration" in Anarchy Online's Shadowlands.