I like the idea of lost magic and am quite curious to see how the healing and blood magic could be utilized in a ttrpg context. If it were a party member, maybe it would attract too much attention to use, therefore the player never truly realizes the potential of their power because every time they try to use this lost magic it alerts the BBEG, either by magical means or word of mouth spreading rumors of a party of adventurers possessing lost magic.

I noticed a minor spelling mistake when talking about Mask;

Mast wears a featureless porcelain mask that completely...

It's funny. (to those reading that are not aware, we are cousins) I've been hearing about Mach'Lithe for over a decade, but never did really get my head around the severing of it from the rest of the world. I always thought of it as more of a Terry Goodkind ghost wall. Even though you described it as looking like an extremely powerful storm. I always figured that if you crossed the "wall" you'd make it to a normal continent that's just severed from the rest of the world.