An MLP/Warhammer 40K Crossover

The Iron Warriors 38th Company has landed in Equestria, entrenching themselves like a barbed hook. They hunt the aliens of the Tau Empire, intent on destruction and pillage.
A small squad is dispatched on a reconnaissance mission, only to find that there is intelligent life on this world besides the feuding space-farers.
Will these improbably adorable and friendly equine aliens turn the damned warriors of Chaos from their blood-soaked path, cleansing them of their dark legacy with the magic of friendship and harmony?

No.
No, that isn't happening.
EXPLOSIONS!!

(Dark humor warning; limited grimdark themes)
(Cover art by Nicholas Kay)
(This series now has its own TVtropes page!)
(This story is a contestant in the Tournament of Canterlot, a charity event to raise money for Syrian refugees! Go here for details and donations!)
(Featured on Equestria Daily 8/20/15 )

“The ultimate fate of the Salamanders' Primarch is a matter of much conjecture, for he disappeared many years after the Horus Heresy. Some sources state that Vulkan led his Chapter for three entire millennia before he departed on some mission he never declared to the Imperium at large, though scant evidence of any of his deeds throughout that age remain. The tale is made all the more mysterious by the fact that Vulkan appeared to have left behind him a text, called the Tome of Fire, within which is locked the nature and location of nine artefacts the Primarch willed to his Chapter. It said that over one thousand standard years after the events of the Horus Heresy, Vulkan hid these nine artefacts around the galaxy for his Chapter to find, as a test to see if they were worthy of his leadership. Of these nine relics, five have been recovered, three of which, the Spear of Vulkan, Kesare's Mantle and the Gauntlet of the Forge, are wielded by the Chapter's Forgefather, Vulkan He’stan. Two, the Chalice of Fire and the Eye of Vulkan, remain on the Nocturnean moon of Prometheus in the Chapter’s fortress-monastery, while the last four artefacts, the Engine of Woes, the Obsidian Chariot, the Unbound Flame and the Song of Entropy, have yet to be discovered. The Tome of Fire claims that only when all of these artefacts are recovered by the Forgefather of the Salamanders, as five now have been, will Vulkan judge the Salamanders sufficiently tempered to have passed the ultimate contest. Then, so the legend states, he shall return to lead the Salamanders in the final war against the enemies of Humanity in accordance with the prophecies written within the Chapter's most sacred tome.”

Hope is the first step on the road to disappointment. The universe is full of hope, as it is with despair.

Far too often will the desperate fools of the universe lay their hands upon the key to their salvation...only to have it snatched away.

So when Ahzek Ahriman of the Thousand Sons encounters such salvation, he does respond with hope, but with determination. He will restore his lost brothers, he will right his ancient wrongs, and he cut down anyone who dares to stand in his way.

This story is a sequel to Equestria, the Infinite, and the Divine

Note: Technically it is a sequel to the other two stories but I am sure it does not need the others to stand with.

Cadance goes to Griffonstone to finalize a trade deal; Shining Armor follows her.

Trazyn abducts her and Armor (for respect) for a quick talk before leaving for good from that cursed rock.

But he did not leave before asking one last question.

One. Last. Jest.

(Because why not, eh?)

This story is a sequel to Double Twilight Love

Following Pearl's unexpected trip to Equestria, Princess Twilight finds herself curious to know more about what the young girl told her about her hobby of tabletop wargaming.

Pearl, always eager to help a new wargamer, is more than happy to get the princess started on a new journey, and Twilight will soon find herself starting a new hobby. And she isn't the only one.

This story is a sequel to The Sun, the Infinite, and the Divine.

Trazyn the Infinite and Orikan the Diviner are back in Equestria. That time, however, Orikan is frustrated. The poor thing is lost in the comprehension of what has happened to the time thingy after Starlight's bizarre adventure with Twilight... and Spike. Yeah... him... Forgot about our little fella.

Anyways, in brief: Orikan is confused about the wibbly-wobbly, timey-wimey stuff caused by magic, and everyone of importance is told about our bombastic duo.

Trazyn and Orikan found themselves stranded in Equestria. Wanting to learn more about that place's hidden history, Trazyn sought Celestia for a talk.

Going to the appropriately named Boring Fields, south of Canterlot, Celestia will discover a slither of the horrors of a foreign - and thankfully separated - universe.

Venerable Dreadnought Stratta, One of the oldest Ancients of the Lamenters Space Marine Chapter is lost in the warp due to a warp jump gone wrong. Though despite what should've happened it seems the chaos gods have other plans...

T rated for now but its subject to change

EDIT: Whoo! we got featured 10/14/2019

A strange accident has stranded three mighty warriors in Equestria: Horus Lupercal, Sanguinius, and the Emperor of Mankind. Trapped in the bodies of ponies, and fresh from the battle on the Vengeful Spirit they must navigate this strange new world. But their very arrival has altered the course of Equestrian history: Nightmare Moon has escaped her end, and still haunts Equestria. With Horus at large with her, and the Emperor crippled by his injuries, Sanguinius must work with Twilight Sparkle to find a way to save the world, while maybe learning a few valuable (and grudging) lessons about friendship.

Warning: Silliness inbound.

By order of the high lords of Terra themselves, a lone soldier from the Death Korps of Krieg has been sent to the planet Epona to wipe out its Xeno population. Starting with Equestria, the Korpsman has sworn not to leave the planet until he falls or completes his mission.

However, no Korpsman should fight without setting up a proper trench first, and so the Korpsman must dig...and dig...and dig.

Destroying Equestria is going to take a while.