Literally, a tarot card simulator. It doesn't get more occult than this.
The entire game makes many references to kabbalah and gnosticism. Note the bloody cross behind the title, that really wasn't an accident.
The game's premise literally hinges around a satanic cult looking to bring their demonic god into the world. As such, there is a lot of occult symbology in the form of magic circles, references to drug use, and ritual sacrifice all throughout the series.
The end boss of the first game "Samael" looks almost exactly like Baphomet, an actual demonic entity in real life occult/freemasonic writings.
Lots of occult terminology/symbology in this one. Freemasonic checkerboard floors, all-seeing eyes, there's a 666 on a bottle of alcohol, and the good guys are referred to as "Nephilim" (odd choice since the Nephilim in the Bible are actually the bad guys). There's also loads of New World Order references and plot points.
From the website Beginningandend.com:
"Another game named after the The Divine Comedy, the protagonist in this game goes into hell in order to resurrect his dead wife. It includes witchcraft, brutal violence, demons and scenes where the hero fights and kills “unbaptized babies.” One of the final missions features Satan in full frontal nudity."
Another game where the heroes are referenced as Nephalem (similar to Nephilim) and are again the offspring of angels and demons (similar to DMC).
Lots of gore and violence in game. The game series as a whole tends to use the names of actual demonic entities ("Looking for Baal?"). In D3 specifically, there are loads of real life occult symbols used for player's banner art such as satanic pentagrams.
If Diablo is just supposed to be a made-up character, why use real life satanic symbology? Why not just design symbols that are made up as well?
Openly acknowledges the illuminati. The first game had quite a lot of predictive programming. The entire series is basically a giant advertisement for transhumanism.
The title seems to be derived from "Deus ex machina" or "god from the machine". Many conspiracy theorists believe the antichrist's kingdom will be heavily infused with technology, where mankind will attempt to make themselves immortal gods via science thus trapping their souls in the physical world forever.
Regardless of how this thing plays out, one thing is certain: Don't accept the mark of the beast.
Numerous occult symbols appear in this game including the all-seeing eye, the pyramid, satanic pentagrams and the triquetra.
That and the main character you play through most of the game kills people for a living but since that's sadly a staple for most video game characters that's no where near a shocking as it probably should be.
One of the most anti-Christian games I've ever played. The entire game presents Christianity as this creepy, racist cult doing very awful things such as forcing people to be baptized before being allowed entrance to the city.
There's also all-seeing eye symbols and transhumanist ideas found throughout the game. It also paints the antichrist as a misunderstood hero since Booker himself is portrayed as the antichrist of this particular religion.
I never had a chance to play this one but the synopsis and pentagram along with the one-eyed salute on the cover art are more than enough to make me find room for it on the list. Description from Beginningandend.com:
"In this game, the hero is a high school boy who survives the apocalypse and awakens transformed into a part-demon, part-human hybrid. His newfound powers and abilities were bestowed by Satan. He uses parasites to summon demonic power in order to fight his missions. Gameplayers are required to negotiate with demonic forces in order to fight battles. Lucifer is portrayed as a friendly, benevolent angel who can be your ally, while Yahweh, the God of the Bible is a “vain, dictator” who has no compassion and is referred to as “the true enemy.” In one of the prequels, the hero’s mission is to hunt down and kill the archangels Michael and Garbiel, both righteous, holy angels in the Bible. In Nocturne the goal is to recreate the world in one where God no longer rules and all people are led by “reason.”
Additionally, in Europe, this game is entitled: Shin Megami Tensei: Lucifer’s Call."