not the arbiter we know and love.

it was a previous arbiter that we have no idea why he is an arbiter.

Because he was a ''Disgraced'' leader of the Covenant, so to ''Claim great honour in Death'' he was to don the ancient armour of the Arbiter; and Elite custom, so that is how Arbiter became Arbiter.

Well in campaign you can play as the arbiter. But you cant play as the arbiter anywhere else.

no such thing of diamond arbiter

They are the same but I like the Arbiter