How do you establish those "codependant feedback loops"?
Well, the answer is different in Monsterhearts, because almost all of the rules drift is about relationships and promises and dependency.
But...
"When someone convinces you to do something, when they really get under your skin and leverage what you want, they mark +1 Hx with you."
+
"When you serve your master without them even having to ask, mark +1 Hx. You anticipated their needs."
That's one way to go about it.
Then, it's about working angles, and being uncomfortably attuned to one another's needs.
Another is to say something like this:
"When your master tells you what to do, if you do it, record it on your List of Duties. The Master suffers -1 to attempting to do any of the stuff on your list of duties."
This is another way to go about it.
Then, it's like: the master has a competent lackey! The lackey is the only one who knows how to purify the water, re-shoe the horse, or mend a tunic. And suddenly, the slave is very important, because the master is debilitated without them.