No mate, going all the way up that side of the illusion tree for quiet casting just for one spell is a waste. Muffle is already very quiet so you don't need quiet casting for it, invisibility is a very noisy spell so you should choose your moment before using it...
No mate, going all the way up that side of the illusion tree for quiet casting just for one spell is a waste. Muffle is already very quiet so you don't need quiet casting for it, invisibility is a very noisy spell so you should choose your moment before using it...