The Arbiter is one of the race known to humans as the Elites - or, in his native Covenant tongue, the Sangheili.  He was once the proud commander of the Covenant Fleet of Particular Justice, but fell from grace when the forces of Earth - aided in no small part by the Master Chief - saw to the destruction of the first Halo installation.  After this, he was stripped of all rank and responsibility, and made to wear the ceremonial armour of the Arbiter, regaining his honour through death in combat.  First an enemy of the Master Chief, the Arbiter came to realise that the Prophets (the San 'Shyuum) who controlled the Covenant were preaching lies; he and the rest of the Sangheili eventually ended up fighting alonside the humans in an attempt to prevent the Covenant from destroying all sentient organic life in the universe.

On DramaDramaDuck, the Arbiter wants to make amends to humankind, having seen the error of his ways and realising the mistakes he has made in the past.  Thus far he has taken a liking to Jason Bourne, sensing in him a shared feeling of regret and redemption.  He is using DramaDramaDuck as a way to learn more about humans, and to let the human race know of his sorrow and regret for his actions of the past.