>>5281786That's mostly up to Malcador's needs and goals.
I like to imagine where the Librarians are soley focused upon the application of the warp for battlefield usage, essentially psychic warriors, the sons we send to Malcador are going to lean more towards the research, application and support roles.
Basically think the difference between a sanctioned battle psyker and the more support based psykers like astropaths, navigators and mechanicus researchers. If you upscaled both to astartes level, librarians would be the former and our sons would be the latter. Assisting in the knowledge department and application of technologies and projects only Malcador and the Emperor would ever approve as well as acting as muscle power to those psychic houses and even a beat stick against demons. Imagine if they could help calm an astropath or navigator undergoing a moment of crisis through a terrible warp storm, rather than falling upon mercy blades or worse succumbing and damning the ship.
Likely they still won't compare to the sheer psychic knowledge of the Thousand Sons and I imagine there will be competition between the Thousand Sons and themselves for influence over the psychic houses (I like to imagine the Thousand Sons were key to winning over many otherwise loyalist navigators and astropath houses and the psychic research elements of the Mechanicus). But they will benefit from direct communion with Malcador, the Emperor, and assistance from Mars and the fact that they were and still will be adepts of the Cult Mechanicus.
Also one thing they have over the Thousand Sons is they don't cavort with demons or tutelaries or spirits if they can avoid it. If directed by Malcador they will bind one and use it as a power source or ritual at his behest, but freely letting them flit about as if they were pets? Fuck that shit.
