the emperor followed the malcador's advice and created his female primarchs. You are a common soldier of the imperial army who is sent to tell the primarch Khana to take her legion and move inmediately to Terra that is under Siege. You find her far away in the segmentum obscurus, despite being loyal she doesn't like her genetic father

Khana: you've come here to deliver a message?, speak, what dirás that man wants from me and My legion?