Despite my meme, I actually do have a few questions.
Who and how would you/someone discover the process of the crystal making
Are we blaming the discovery on 'experimentation' like everything else or will it actually have solid RP behind it's discovery(say, an event or something.)
Can't mages already not wear fitted plate without being tired?
Aren't mages already easily injured?
Mages have never been able to wear full-plate armor by the time they reach mid T3 without exhaustion?
You do realize that giving someone a constant connection to the void with a simple ritual that's available to anyone who reaches T5 in a single magic is subject to extreme power-gaming?
How do you plan on preventing powergaming from happening? If it requires an MArt, they can simply get past that then PG the shite out of the tool and most nobody would report it.
Keep in mind this is coming from a rather learned Mage player, who's encountered several other players with Magic that'd abused lore like this in the past and miraculously haven't been blacklisted, some even still having magic after one or two years and still power-gaming to this day.
Otherwise, I think the lore looks great and it has a bunch of good ideas behind it but I'd suggest self-denying your own lore and getting someone to help you fix all the loopholes and gaping holes of missing lore and clarifications, because you contradict yourself numerous times in your own writing. Good luck!