Games Workshop has a new 40k Campaign Pack that they've posted on their website. This one sees the Iron Warriors face off against the Imperial Fists at the Siege of Hydra Cordatus. It's got a scenario for you, as well as background history, and a set of unit stats, the Dominator Cohort.
From the article:
We’ve already shared the rules for fighting The Battle of Pluto and The Defence of Sotha in the Age of Darkness. In the next part of our series of exemplary battles for The Horus Heresy, you can play out the brutal conflict between the Iron Warriors and the Imperial Fists at the Siege of Hydra Cordatus.
As with the previous campaign packs, this one comes with background on the battle, new missions to try out, and a new unit – in this case, the Dominator Cohort* for the Iron Warriors. Here’s Andy Hoare from the Horus Heresy team to tell us all about the latest campaign.