General Grievous, Supreme Commander of the Separatist Droid Army, conqueror of star systems, and slayer of Jedi. And... stranded on Equestria?

This can't end well.

TV Tropes page.

Now featuring a dramatic reading by LimeyPony!

King Sombra’s dark influence was obliterated by the Crystal Heart, and the villain is well and truly dead. But when he attempts to steal the afterlife of an innocent victim, a human spirit is left hurtling towards Equestria, where this unfortunate soul is revived into the only vessel available: the reconstituted body of King Sombra himself.

Thus, a cheerfully oblivious alien is crammed into the form of the most evil and malicious being Equestria has ever known. Not that Shining Armor and Cadence know this, of course. As far as they are concerned, the King is back and he’s lost his fricking mind.

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After a mishap involving the Transportalponder, the Courier finds himself in a place he doesn't recognize. With no way back and nothing else to do, he decides that wandering into the nearest town is the best option. Being the Courier, things aren't that simple...

A Fallout: New Vegas/My Little Pony: Friendship is Magic crossover

The style alternates between omnipresent third-person and the Courier recounting his tale to... Well, take a guess.