The Horus Heresy takes 40k back to the… well, the Horus Heresy. Games Workshop has posted up a new FAQ for the iteration of the game, as well as free rules for old Solar Auzilia units that have been around for quite a while. You can head over and download both now.
From the article:
The Liber Imperium army book is now available in North America, so the time is right for a new Legacies of the Age of Darkness documenting classic Solar Auxilia engines and attachés.
These are free bonus PDFs, bringing rules for units that didn’t get featured in that faction’s supplement – from mighty plastic tanks to beloved resin war machines. Fittingly, Andy Hoare from the Horus Heresy team has some thoughts.