From my experiments on MonMagic I can tell that not only Race/RaceImg is responsible for Magic attacks but also Appr. Try moving NumaMage ( on my server ), in Korean files it will be appr 184. When u move it to Appr 174 the mob (Race + RaceImg the same) it will not generate MonMagic.
Maybe I did something wrong correct me, if I am.
IMO MonMagic is attached to Appr and it is written somewhere in client. MInfo.Dat have some numbers but how it works ? Only God and WebZen knows atm :P