Legion20
Imagine Lith on day learns to control it and manages allow single demons/spirits to enter him. Maybe it would be a cheat like power where he could see all of their memories and learn tons of stuff just by having spirits enter him. sure everytime it would be an extreme strain on his mental faculties because he lives through all the pain and the lives that couldn't move on after dying but hey it's not like he of all people is new to that. so I think with a lot of rest inbetween and good emotional support from friends and family he should be fine and have a great source of knowledge that noone else has. đ€
My guess is that he wIll not be able to train each form separately as he will be limited to what each form can do, i mean its been mentioned a lot that mogar only cares about the balance. So he would have to train in his Tiamat form for each of his natures to contribute something to keep the balance just how he evolved.