My name is Chao Lingshen.
In my short lifetime, I have traveled the stars. I have traveled across hundreds of years and interacted with dozens of generations. I was born a child of rebels, insurrectionist mages fighting against the United Nations. They sent me to the future to get revenge, but I found my purpose instead. Instead of revenge, I became a protector. Technology and magic were my weapons, but I was only one person. Against a pan-galactic Covenant, I was all but singularly powerless.
In my short lifetime, I have seen war. I have seen suffering, chaos, and devastation. I have caused some of it, and I have fought to end it all. Over the years, I worked to integrate magic into the normal routines of society and combine it with future technology, and then returned to that future to finish what I had started. And between magic, science, and the human will to survive, we succeeded. We won. The human race would survive as a species.
I knew from the beginning that I would be making a new world. Or a new existence, a new dimension, a new timeline. An alternate reality, the same and yet distinct from the one I had known. Simply by existing in the past, events altered. The moment I appeared in the past, that time in the year 1997 which I still do not know the exact date of, the history of the future—my 'past,' as it were—was lost to me, replaced by a new reality. It's the Heisenberg uncertainty principle, you see; one cannot study an object without affecting it.
As much of an ego-case as it makes me sound, you could really say that I caused this dimension to exist, and I have since taken it upon myself to bear the burden to ensure that it is protected, that its inhabitants are free to live the lives they desire without a threat of utter annihilation, internal or external. I've become quite fond of this dimension, the friends I've made, and the comrades I have fought beside. To me, even though it is not truly my native dimension, it is still my home, the Prime.
Having vanquished the threat of the Covenant, many people would rest, lay down the mantle, and let someone else carry the burden of the Prime's protection. I cannot, in good faith, allow myself to do so. Stopping one extinction-level event doesn't guarantee there won't be others. And that is why I do what I do. Penance? Perhaps. Selfish lust for adventure? Possibly. A megalomaniacal desire to possess all of the most powerful technologies I can come across for my own sole use? Maybe even seriously.
In my short lifetime, I have had a direct hand in saving the human race three times. I have worked behind the scenes or to less overt effect dozens more times. It is my self-appointed journey, my personal millstone. I have had the hubris it took to think myself above the rules of time and space, and so in payment, I have chosen this dimension I have shaped as my charge, and I will protect its existence. At the cost of life and sanity, I will stand in the path of any threat and declare,
"This world and those who reside in it are under the veil of my protection. If you still wish them harm, then come and face the wrath of the Timesnatcher."