Warhammer 40k - Titan Graphic Novel by Dan Abnett, Anthony Williams and Andy Lanning

When the ageing commander of the Warlord-class Battle Titan Imperius Dictatio dies in the heat of battle, it falls to Cadet Princeps Erwin Hekate to take control of the mighty war machine and save it – and his comrades – from certain destruction. Fusing his mind with the spirit of Imperius Dictatio and bending the construct to his will, Hekate takes the towering Titan into battle against the foes of the Imperium.

(These are all the Titan Comics I have. I'm sorry if this isn't the complete series but it's all I can work with.)