The Guardian Of Equestria 2: The Doom Slayer (DOOM X MLP)

Tempest Shadow had heard the rumors. Stories, told in frightened whispers by traders and wanderers, in the taverns and around campfires. The stories told of an almighty champion, a monstrous creature from far beyond the stars, that had come to defend Equestria from its enemies. The stories told it had slain dragons by the hundreds, broke the savage beasts of the Everfree like twigs beneath its boots, and torn down titans and monsters alike with its wrath. They said it wielded weapons that could turn mountains into gravel, and seas into desert. That it was clad in armor, that neither the sharpest blades, nor the mightiest magics, could pierce. The rumors said it was unstoppable, relentless, beyond the power of mare or beast to oppose, that it was. . . a god. Tempest had laughed at the rumors and stories, as she flew toward Equestria at the head of an armada, intent on the conquest of her weakling former homeland. Never once did she give the obviously absurd campfire tales even the slightest credence.

The arrogance of fools and tyrants, shall awaken the rage of a monster, and lead an empire, to its DOOM. . . .

I do not own this story, al credit goes to Thule117 on FimFiction.