For as long as the oldest of them could remember, the Guardians had defended what remains of humanity against the forces lurking in the dark. With gun, blade and the Traveller's Light, the heroes born of Earth put themselves between the monsters from the void and those too weak to fight back. Human, Awoken, Exo; the physical coil of the Guardian had never truly mattered so long as they were willing and capable of defend their homeworld.

Until a Guardian came from the wastes that was neither Human, Awoken or Exo; a Guardian not born of Earth.

(Destiny/FiM Crossover)
(Gore tag for blood and violence)
(Thanks to Noble Cause, BradTheBrony and Metallusionsismagic for prereading!)
(Possible Spoilers in the comments, BEWARE!)