Compatibility
The cards are compatible with the later Dark Millennium collectible card game also published by Sabertooth Games. Loyalist cards from Horus Heresy may be mixed with "Imperial" cards from Dark Millennium, while Traitor cards may be mixed with "Chaos" cards. Unaligned Horus Heresy cards can be used with either of the two, but not with new Dark Millennium types such as the "Ork" and "Eldar" decks. Any mixed decks are legal Dark Millennium Imperial or Chaos decks, but they are not legal in Horus Heresy.
Cards from the older Warhammer 40,000 Collectible Card Game are semi-compatible with Horus Heresy, requiring rule changes in order to work with the new game system.
Read more about this topic: Horus Heresy (card Game)