Roboute Guilliman, Primarch of the traitor legion of the ultramarines, Blade of Chaos undivided.

Guilliman was tricked by his brother Lion El'jonson, the Warmaster, into believing some of his brothers have turned traitor and have imprisoned their father, the Emperor of Mankind on holy Terra.

Guilliman's trust and love for his brother made him believe the Lion's lies as he unknowningly betrayed the Emperor and took the Lion's side, marching for holy Terra in a false attempt to rescue their father.

Guilliman sees chaos as a tool and is willing to use it but refuses to succumb to it like some of his brothers.

Now, Guilliman and Lionel march towards Holy Terra alongside their traitor brothers and their legions, tearing through and decimating any and all foes that oppose them.