The Arbiter. That is merely his title, nothing more. He has no name, no family, and no future... until now.
This Arbiter, he who was born of hate and wrath, thought no creature, let alone a mere human, could ever best him in combat. But, he was wrong. In the events of the Halo wars campaign, the Arbiter fought sergeant Forge multiple times, each time suffering a heavier, more degrading defeat. And at last, just when he thought he had the pestilent human, the gods suddenly turned their wrath upon him for his failures, and he failed against the little human, and perished on the shield world containing the forerunner fleet... or so he thought.
The gods he followed may have forsaken him on that day, but another, more fun power gave him another chance, to begin again, in a new world of its choice. However, that power failed to specify the Arbiter's new purpose, and dumped the belligerent sangheilli into a world that tests his very patience every moment of every day. Will he finally discover the source of true peace here, in this colorful, pony-filled world, or will he burn the fetid, cutesy, scum-sucking, human-loving planet to its bedrock!?
...Probably the latter.