Elbows wrote:The
FAQ states that models may be considered <DEATH GUARD> if they are <NURGLE> marked, more or less.
Quote:
You can only choose for a unit to be from the Death
Guard Legion if it has the Nurgle keyword, or if it
has the <Mark of Chaos> keyword and you choose
to replace that with Nurgle. You cannot choose for
a Hellforged Rapier Battery, a Chaos Hellwright or
a Chaos Hellwright on Dark Abeyant to be from the
Death Guard.
EDIT: In addition, the latest beta rules more or less state that a detachment may contain any units as long as they share a common keyword which is not <CHAOS>. The Hellforged Contemptor contains <MARK OF CHAOS>, Heretic Astartes, and <LEGION>. So as long as those match your Death Guard detachment faction keywords, you're good. At least that's how I read it.
First part, you're correct. You just choose the Contemptor <legion> to be Death Guard and put them in any detachment you like, job done.
The Edit part is kind of right, in that you can make a detachment using any keywords, so all units being <Nurgle> would be a valid detachment... but if they aren't ALL <Death Guard> then you lose your legion trait, so it's worth keeping an eye on.
But basically it doesn't matter in your case, just take <Death Guard> <Nurgle> Contemptors and call it a day.