He’s never been more serious.

Magnus’ face is saying “I dare you. I dare you to go on with this nonsense right in front of me. I dare you to ignore what I’m making you feel just by being in the same room as you and commit yourself, soul and body, to someone else that you can never love. Not like you love me. Not like I love you. Go on. Do it in front of me or don’t do it at all.”