Maverick was wondering if you could “rule the world” at the side of William Mortimer, as one user put it. He tried all scenarios and is sharing his findings here.
The short answer is that there is no scenario in which you and Lord William Mortimer both get a happy ending. Either he will take you out or you will take him out.
If you do follow him all the way through, he will be very impressed with you. This makes him want your body even more as his next vessel, however. This ends in a confrontation that will not end well for at least one of you either way. Lord Mortimer’s goal for the conference was to have his children gather, then pick the most suitable as his next vessel.
He is not overly antagonistic when he makes his final move against you. It’s more of a “nothing personal, let’s not be dramatic” thing. In some of the endings, he even shows his pride when you outmaneuver him to take him out. It still comes down to a “It’s either you or him” scenario, however, so don’t give up your Holy Lance to him.