So, when Lamia's sucking the life out of Richard, the Marquis appears just in time, right? And he drags her off and threatens to break her neck if she doesn't give Richard's life back, so of course she does. But since when did the Marquis do anything if there wasn't something in it for him?
And OK, you could make the point that he needs Richard alive to help him complete the quest. But when Richard's got his life back and is safe, the Marquis then threatens to kill Lamia and all her kind by burning down their cave, if any of them try to harm Richard ever again. Why would he do that? Richard won't be any more use to him after Door is safe and the quest's done. Unless he actively doesn't want Richard to die - not just at the moment when he's needed, but at all. Which, to my admittedly biased interpretation, means he must be coming to care for him. Slashiness!
