Roderick milks Imogen's breasts to keep his grip on the throne.
She yields to his commands in the torchlit vaults because the partnership secures her place. The power gap means she must submit to his obsession with her milk.
Every time they are alone in the study, he orders her to bare her breasts for his mouth. He suckles and expresses her milk across the desk while claiming her body. The pattern escalates with each new deadline and each new risk from rivals. The milk spills as he degrades her under his authority.
Discovery would shatter the succession and their fragile bond. She stays anyway.
His fingers find the laces of her bodice.