Liches are realists, above all else. The lich transformation removes the capacity for any of the strong emotions, so they can no longer experience hatred or anything like that. The lich is in your party simply because they respect power above all things, and the members of your party are nothing if not powerful. A lich is also completely self-centred, and taking this with the lack of emotion, they would be totally uninterested in anyone who has nothing to offer them. They remind me of some senior managers, even to the expressionless, fleshless faces... 
