User blog comment:SniperGhost/Death Before Dishonor/@comment-1932673-20100611105742

I don't think so, Zarkreus is a Chapter Master whilst Oberon is a Captain, plus Zarkreus as a Doom Herald will have access to some secret psychic powers availble only to the Doom Heralds (In many aspects the Grey Knights and Doom Heralds are two faces of the same coin, one light, the other dark.)