Nearly 3/4 of humanity has either been converted or executed by the so called "Princess Celestia", claiming that she will drive out the corruption of man by converting them into ponies. Her scout's reported her, that humanity has taken refuge in an abandon town of Voi, near the abandoned city of Mombasa. She smiled towards their resistance towards their own extinction, but little did she know, they were preparing something far bigger than anypony could imagine.

A Halo x TCB: Xenolestia crossover (and don't worry, they will only have the spartan's and another thing ;)