The Ur-Didact did not die in his last encounter with Master Chief over Earth. He fell into a slipspace rupture and crash landed on the planet of Equestria.

Eager to find a way to reunite with his armada, he ends up having to befriend some strange, overly hospitable creatures, and becomes more involved in their lives and world than he bargained for, and gets dragged into many bizarre situations. Perhaps being stranded on this planet and meeting this strange race of ponies is just what The Didact needed to be reminded what beauty lies in the variety of life in the universe. But then when an old threat returns to Equestria, The Didact must not only defend the strange planet from it, but also from another, much greater threat he may have inadvertently caused.

Meanwhile, the Humans and Sangheili join forces once more to combat the threat of the Forerunners. How will the Forerunners fair without their leader? How will the Master Chief and the Arbiter fair?

Warning: Spoilers for Halo 4.
Disclaimer: I do not own MLP or Halo. I do not profit from this story.