If you want to, maybe try to put postUnitCombat function to relevant units from Winter Court, making them abduct slave on this function (like Mimic's stealing promotion)? I am not sure this would work, though. But personally, I am fine with every units during Winter Court can create slave. One thing I forgot to mention in previous posts: does this mechanic create double slave if the unit has slavery promotion/Slavery civic active? That's cool! Have you try to run AI against Winter Court, to see how they react with the damage? I'd love to! Let's see what will happen during your test and think the best way to code this into Xtended.