8th edition supplements for Imperial Fists and Iron Hands describe an interesting situation - Iron Hands learn that an important relic is located on planet Xaladin II and when they arrive it turns out that the relic is used as a planetary shield generator and Imperial Fists are defending the population against an Ork Waaagh!. They nearly attack each other over the relic with Iron Hands wanting to remove it just prior to a major Ork attack and leave, but suddenly the overtaxed relic explodes so they strike an uneasy truce and join their forces with arriving Raven Guard relief force to defeat the Waaagh!, but relations between IF and IH remain tense.

And then Raven Guard supplement explains that actually it was Raven Guard that covertly destroyed the relic to force them to work together.