Their first encounter came against the Dusk Raiders on Fort Sparcos. Unhappy with their refusal to cooperate with their Chaos brethren and disturbed by an earlier attack on the encumbent Iron Warriors force in the sector, the force set about raiding the Dusk Raiders' supplies and teaching them a lesson. Unfortunately their enemy was wise to this fact and defended their positions admirably, forcing the new Iron Warriors force to seek their vengeance elsewhere.
While their leader was having a set-to with the Dusk Raiders a second force attempted to opportunistically raid the Trebbians defending the fort itself. They underestimated the Trebbian defences however and were similarly defeated, leaving the Iron Warriors fuming. The force left the Sparcos system on 1103.009M32 and set course for the Rim Worlds.
Their first visit was to Typhon, where the Night Lords were putting the finishing touches to their new city "Rim World Prime", built from slave labour and intended to rival the cities of the Imperium. It was in effect the first part of their plan to reconstruct their own Imperium by their own rules, and the Night Lords did not appreciate the arrival of the new Iron Warriors force. After a brief angry encounter between the leaders of the forces, battle soon commenced.
If the Iron Warriors had intended to take the small planet for themselves they had underestimated the Night Lords' will to defend their new Empire, and once again the Iron Warriors were defeated with no new information and no secure base from which to launch their raids. It had been a hard shock to the system, but they had at least discovered that in general, the other Chaos forces were generally hostile to the Iron Warriors in general, who they blamed, often innacurately for failures on Aleph 4 and Tarsis Major.