Kaos is the lesser known fifth rider of the Apocraypse. He is obscure as he left the group before their fame but does not hold any emotion towards that fact.
He is later discovered to be Ronnie Soak, a milkman who also specialises in other milk products like yoghurt or rancid yak butter from 5,000 years earlier. The name Soak is a reversal of Kaos. Though Death does not call upon him, he still rides out to join the other Horsemen in their fight against the Auditors of Reality.
His name is a play on chaos, who he claims is a form of kaos dressed up in a suit.