It's 2 AM on a weekday.

You should be asleep, But the sounds of battle and the churning of the megacity around you has your brain stuck in a daze. An 10 foot hulk named "Dad" wearing nothing but a nightcap and leopardprint pants keeps mowing through hordes of people with a giant industrial pipe yelling something about "Rashuns", and a frail old man ranting about his "beloved" just popped a giant slugs brain like a ripe tomato before casting blue flames from his hands toward "Dad" who is now neck-deep in gore.
A pack of mutated dogs jump out of a nearby closet begin cycle-tackling Dad to the ground as some crazy pirate lady who's been rambling about a place called "Cadia" hands you an ammo box and screams out "For the emperor!" stabbing herself with a needle and charging blindly into the dogs before 6 consecutive suicide bombers collapse in on them both, wiping out half of your squad in an instant.
You're nudged by your old man friend pointing towards a glowing green book in a random alley, before picking it up and instantly eating 1/2 of your health. He cackles like a madman as he runs off down the dank alleyways, as glowing blue lights and the screams of men and women echo out into the cityscape beyond.

It is the 41st millenium, for 10,000 years the Imperium has dominated the galaxy, now we know how. Welcome to Darktide