i only remember a couple of details. i think the main character gave up magic because someone got hurt, i want to say his powers were bound or something.

there is a part where he casts a spell to become invisible but it only works if he is completely still. Someone thinks he's in the room and cast some blue haze that slowly fills the room revealing his outline.

the book is right at the edge of my memory but i remember liking it and wishing I could read the whole series. it think this was book 3 or something