Magnus and Luke The downworlders series continued.

Shadowhunters- 1x06- Clary and Simon bring injured Luke to Magnus- Clip- - YouTube 

 The question is how much Magnus knows about Luke, Joslyn, and the other Shadowhunters, and what they do. As he knows the Shadow World and where did the deep mistrust come from as in the books he has had Shadowhunters living with him and him actively working with the Clave in the past. 

Magnus Bane | The Shadowhunters' Wiki | Fandom 

 In the show, Magnus seems to have a deep mistrust of Shadowhunters and isn't welcome in the institute, yet in the past when he was living in London, he references this in the show that he was deeply unhappy with where he was at. So he moved to New York, and started again, he seems to have a good relationship with Luke in the show, yet we see that Magus seems to know Luke and his history with Valentine and the Circle.  We also see how he became a Downworlder and this seems to be where Magnus's relationship with Luke has become more cordial as they are in the show called the downworlders council meeting, in the books it is the representative of the  Children of Lilith. 

The question is how much did Magnus know and see it play out in real-time. As Ragnar Fell was helping Joslyn and Clary.  Magnus was also helping Joslyn and then it is his relationship with the other Warlocks and Downworlders is quite complex as he is immortal and sees that things change over the centuries he has lived. So how does that change the way that he sees the world?  

We see Luke come to Magnus when he needs help or advice from another Downworlder and we also see Luke help Magnus navigate his relationship with Alec.  

Luke Garroway | The Shadowhunters' Wiki | Fandom 

Shadowhunters 2x17 Luke Tells Magnus About Alec Lies "Season 2 Episode 17 - YouTube - Magnus has over-the-top reactions and starts to doubt Alec as in the show Magnus's main ties to the Shadowhunters are Clary and Alec.  Yet with the Downworld we see that Mangus is very well connected to the Downworld, and his position seems to be political, in the show in books it is different but always seems to be a political one as we see Magnus draft legal documents, sort out disputes between the Downworlders and yes using his powers to heal.  We also see the relationships between Magnus and the other Downworlders and that some of the Shadowhunters seem to know how to exploit this, like punishing downworlders Mangus has helped to get to Magnus and the Shadowhunters seem to know that it isn't great to attack Mangus directly and this is why the rules and attitudes towards Downworlders existed. 

Shadowhunters 2x19 | Magnus, Luke & Raphael - YouTube  - Luke sees through Magnus drinking he is mad at Alec, Magnus's alliance switching with the Seely queen is an interesting move as the others see that she is just as bad in her own way,  Seelie's can't lie but as is said in other episodes they can manipulate the truth, and this is an interesting observation about being a woman with a strong point of view. Luke knows that there is always a catch. 

Shadowhunters 2x14 Magnus Alec with Luke Raphael Meliorn Cabinet Meeting Season 2 Episode 14 - YouTube  - Luke gets upset that he can't appeal for Valentine to be executed, they all have a reason to want him dead, As they said Alec isn't the first one to try this cabinet, and it seems to work due to the way that general attitudes towards downworlders have been treated and this has improved. 

Shadowhunters 2x14 Alec Frees Luke - Talk about Mole in the Institute Season 2 Episode 14 - YouTube   Alec frees Luke due to wanting to have a real change in the way that the institute is run and the Clave is run.