Why not make it so instead of being forced to do what the Borer says, you could add some lore in the initial text saying you've had it for a long enough time to the point you don't even know anything is wrong with you, that you are more coerced into doing what it says, sort of like Vampire charm aura thingie. You're not bound to it, but it's like a trusted voiced in your head. Feels more fitting then being tied to following without character choice. Just an idea. When I was first a borer thrall I just pretended it was my own thoughts and subtly went along with things until it started forcing me to do things my character wouldn't normally do. When it took over and started zombie walking at armed officers all horde like I fought it so I could run away. There RP from both this little fucker inside my head and myself that was really enjoyable by doing it that way. There's a lot of RP you can get when someone is literally tied to you and you both have different objectives and mindsets.