The Grey Knights are here?

Just loaded into the mourningstar and heard Dukane's attendant talking about "Knight Commander Draigo". Chapter Master Draigo? Atoma isn't a big enough deal to warrant imperial reinforcements beyond a commissar to train us, but it is a big enough deal that the Supreme Chapter Master of the Grey Knights is here personally commanding forces we have yet to see?

Edit: Marsett is saying Dragor not Draigo. No grey knights.