A meteor impacts the nation of Equestria, Planet Equis. Tranquility is quickly snuffed out when a poison begins to spread violently. The Princesses cannot combat this unknown threat, as no knowledge of it exists. Help comes from an unexpected source.
MLP/Warhammer 40K crossover, part 5. The pieces are placed. The battle lines have been drawn. The 38th Company and Equestria fight relentlessly against the alien menace (the other one, that is), but the odds are hardly in their favor.
A machine built for exploring new worlds and preparing them for possible coloization. A land of magic and friendship that has not seen the blight of war in over a thousand years. This is what happens when the two come crashing together.
An Evil (the capital E is important) long forgotten to the world stirs once more, summoning forth a new Overlord that the races and kingdoms of Equestria and beyond have never before experienced.
[RGRE] An inexperienced unicorn and her human bodyguard travel to the dangerous heart of Preunification Equestria. This "alicorn" filly better be worth it.
400 years before the Unification, Earth ponies are hardly better than slaves to Unicorns and Pegasi. Then a strange, wounded biped is found near their village. With a sign from the gods and the stranger's knowledge, a change begins to take root.