This was the first time I'd been asked to illustrate any of the Primarchs and I was very nervous about doing so. As a fan I'd always wanted to see the Primarchs in all their glory. The only thing was they had to be far away in the background, having a fight.
On Ferrus Manus' back I wanted a big old-fashioned diesel engine to suggest his mechanical nature. It was great fun to do and also have a chance to add a dreadnought and some vehicles in there.
Trivia: Some have suggested Ferrus Manus' backpack looks like a beer barrel, I guess that means he'll never get thirsty.