You know I didn’t really realize at first but the fifth house falls into one of my favourite troupes which is kindhearted , good intentioned, manipulator.
I love a character that can be so nice and so gentle and so caring that you don’t realize how much they are influencing you and it isn’t an act. They genuinely like and care for you.
I’m sure Magnus looked at Gideon and saw a guarded girl who needed some people to be nice to her. He was probably also thinking about the political boon it would be to have an in with the Ninth House.
There’s a reason why Magnus was chosen to be Abigail’s cavalier. It’s not because he is a good swordsmen, it’s because the Fifth is a house that deals in politics and he’s a master at being likeable. The fifth battles in smiles and gold and niceties and Magnus Quinn is the best cavalier for that job. So genuine and caring that even the audience forgets he has motivations except being the funny man that makes you feel safe.