[bluntpencil]

@ Maglag:

Grey Knights aren't sorcerers, they're psykers. Big difference.

A psyker can be pure, a sorcerer actively uses corrupt Warp energies.

It's actually explained better in Warhammer Fantasy, which works differently, I know. In Warhammer Fantasy, Dark Magic=Sorcery. Of course, all magic is dangerous, Chaotic crap, but Dark Magic/Sorcery actually involve arcane deals with daemons and forbidden rites.

@Cheesegear:

And surely, using the Emperor's DNA would require magic? And surely, since Corax is the Emperor's son, he has the Emperor's DNA in his own blood? Also, we have samples of the Emperor's blood kicking around, too, if we know where to look. (On Dorn's armour, on the Emperor's armour (apparently in every suit of Terminator Armour), on the Talon of Horus, on the Throne...)

Of course, I'm asking too much for scientific sense here, I think! :D