Q: If my army is led by a Chaos Space Marines Warlord, and
I have a Detachment of Death Guard, can I use the Gifts of
Decay Death Guard Stratagem to include a Relic on a Death
Guard Character?
A: Yes. The only requirement to have access to
Stratagems is that you have a Detachment of the
appropriate Faction. If you have a Death Guard
Detachment, you have access to their Stratagems.
FAQ DG. Этому ответу уже, емнип, полгода. И он актуален.
И полгода никого не удивляет что берут стратагемами релики неварлордовской фракции.