I considered the possibility of attacking it after it transferred to someone tankier, but I see three reasons not to.

First, it can coup de grace you; even if it failed to kill, it would maim the character horribly until we managed to find something to remove the drain, seeing as it’d be 2d8 (average of 9) constitution drain. Second, seeing as the captain only seemed able to directly attack it on a counter, my character may've been the only one who could potentially damage it unless it retaliated or stopped possession, and even if it was heavily weakened, it’s still a dread wraith, so things would probably go badly. Lastly, assuming its alignment isn’t changed, it is lawful, so letting the deal run its course allows us to avoid dealing with the high chance of a character death.