Question About Mastering a Spell College

If I get full 5 ranks of a specific spell college, do I achieve automatic mastery of that college and only that college or do I have to quest to choose what college I want to master? I had heard that when you master a single spell college you get like halved fatigue costs for spells with that college. I don't want to max out the wrong college first if it's automatic. And if you have to quest for it, any tips on where to start looking for said quest?

 

There is a city of Mages that you come across in the main plot of the game.
The masters are all in there and will give you a small quest to gain your mastery.
And yes you can only gain one mastery and it does half your fatigue costs.

 

holy shit that mean i can cast desintegrate all the time

 

Too bad you only get one.

 

Plus u cannot disintegrate the Final boss

I tried disintegrate on the First Necromancer at 100% Magical Aptitude, but it just fizzle out.

Anyway, I get scared whenever Dante disintegrate enemies coz no more loot, esp if they got a key or quest item.