I'm Cortana, and I am Chief's A.I. His Artificial Intelligence. I run throughout his system and tell him what need to be done. He can't do anything without me.
I, the Arbiter a betrayer to my own race is friend to John. I realized the opponents are doing right. I joined John and annihilated my own planet. I have no regrets.
Well darn,Sierra is the best one out there. Everyone wants to be spartan and he makes it look easy, but I still remember when he let 343 guilty spark fire a beam at me.