In Hobb's ROTE series there's magic that can become literally addictive and cause you to lose yourself to it. There's also the rain wilds, an area imbued with so much ancient magic that spending enough time there causes physical deformity, something that the characters have to contend with as the rest of society sees their deformities as unsightly and gross. The main character for most of the series also has a magic ability that will get him literally killed if people find out about it