From the website:
A strange fate binds Roboute Guilliman, Grand Master Voldus and the Fallen Angel Cypher together. They walk a path of providence; though whether it ends in damnation or deliverance, none can say. On the battlefield, this triumvirate of warriors is an unstoppable, inspiring force, bolstering the morale of those they lead while shattering enemy lines with their staggering strength. Cypher’s pistols roar as Voldus’ psychic powers lash out – all the while, Guilliman strides like a reborn god, bellowing rallying cries and striking down countless foes.