Some information on the coming Horus Heresy novel Vengeful Spirit has been released, along with this;
Horus looks badass as usual, and I can't wait to see the full cover spread with the Sons of Horus backing him up and the Vengeful Spirit hovering in the background. I've included what info I could find about the Battle of Molech, which appeared only in WD 190 apparantely.Molech said:Molech - Imperial Titan Legions (unnamed, 3) and Imperial Army (unnamed, 100+ regiment) vs. Renegade forces including Traitor Knights of House Devine.
This fits nicely with the small amount of known background for Molech - where the mechanicus knight household Devine betrays the emperor and switches sides, becoming the first Slaaneshi Hell knights and scout titans.