1984
Grimdark has always been a concept of humanity living in the worst environment as possible, and there is not even a single joy can be found in grimdark. 1984 is such example of grimdark. It is a novel by George Orwell published in 1949. It is primary about what happen if the government has the complete control of everyone, where you will be watched everyday and being forced to do what the government said, or else you'll be vaporised. This book is basically the inspiration to all grimdark, including warhammer 40k.
Plot
A guy name Winston wasn't happy about his life. He is sick of doing the same thing, exhausting at work and not having enough to eat. But his life changed when he met Julia, who gives him what he want, which is something the party is unacceptable with. Winston had a fun time fucking Julia, learning about the past and eating the real food from the party, until he was caught by the thought police and was sent to brainwashed. O'brien, who was Winston's boss, is actually an agent from the party. He tortured Winston, then sent him to room 101 to meet his fear. In the end, Winston returned to normal and believes 2+2=5.
few grimdark elements that the warhammer 40k inspired from 1984
-The Big Brother: Big Brother is basically a non-existence figure head created by the fellow jews for those poor bastards to worship. Like many religions, gods are non-existence bullshit that were created to waste your time in.BLAM!! HERESY!!! excepts the Emperor.
-Constant Surveillance: In 1984, there are these shitty TV's that were created to stalk you and troll you everyday call the "telescreen". You cannot turning in off, and even if you do turning it off, you will be capture by thought police and getting your ass beaten. There are other surveillance like helicopters (for tall apartment building), thought polices, and even your own children (damn government bribed them with candy). In warhammer 40k, there are inquisitions that have psykers reading people's mind everyday, and Adeptus Arbites who serve fair justice to common citizens everyday.
-Warfare: In 1984, war is the best way for Oceania to boost their Jew golds, since having unnecessary war with friendly country can not only having their resource, but also to have their land, just so they can build more 1000 meters high city prison for your grandmother to live in. But the Oceania eventually spent most of their money on building more flying metal boxes instead of giving benefits to their own people.