- The death of the Emperor. While the event and the immediate reactions to it are Nightmare Fuel enough, (especially for imperial citizens) what it leads to are the true stuff of horror.
- His first words in several millenia (addressed to his killer, Cypher) are also his last: "End This".
- The most obvious and immediate effect of his death is the shattering of the Imperium into a bunch of so called “petty” Imperiums, each with their own little quirks.
- The birth of the Star Child, who by gorging upon the Astronomicon, eventually becomes the Star Father, the Chaos God of Order.
- The transformation of Holy Terra and most of the solar system into a Daemon world.
- The release of the Void Dragon.
- The Astartes free companies - you know the Training from Hell that molded them into the infamous Super Soldiers they are? Now imagine them set loose upon the galaxy with their ties of fealty released. The result: an unstoppable mob of psychopaths in most places and guns for hire in others, with little difference between themselves and their Chaotic brethren.
- In their zeal, the Black Templars decide that mankind has failed the Emperor and decided to wage a crusade against everything, drawing Space Marines and Imperial Guard remnants they meet along the way.
- Of the Petty Imperiums, the most obviously horrifying would be the theocratic ‘Ophelian’ Imperium. Beginning with the leader of the Ministorum fleeing to Ophelia and recalling the Sisters of Battle, the Government quickly begins a fanatical Witch Hunt that only ends when a little girl is killed after kissing the feet of the Eccliesiarch.
- Good god, the New Devourer. An ork/nid race that make it's two originators look fluffy and playful. In it's wake, the galaxy is mostly full of dead worlds because anything it came across it ate. Even targets the nids couldn't crack were easy meat. After accomplishing this, the New Devourer packed it's bags and left. Why? Nobody knows, but it's probably safe to assume it's really, really bad when the light from the galaxy they were last seen heading to starts fading.
- The Nex. Not much is known about it, but it lives deeper in the warp than even the Chaos gods, and just mentioning it's name causes the speaker to begin vomiting and speaking in an unknown language.
- The Tersis was a ship filled with psykers that becomes lost in the deepest levels of the Warp, somehow came into contact with the Nex itself and emerges different. "What lies within, we fear not ask" indeed.
Nightmare Fuel / The Shape of the Nightmare to Come
One of the few fics that can claim to be a Dark Fic for the franchise Warhammer 40,000 The Shape Of The Nightmare To Come and its sequel are themselves chock full of nightmare fuel. Here are some of the highlights.