Mg skill tree problem

I HAVE MG THEN I PUT POINT IN SKILLS BUT WHEN IM GOING TO PUT ICE STREGHTENER IT SHOWING THAT I NEED "ICE SKILL" WHAT WILL BE THE SCROLL FOR ICE OF MG?

PLEASE SEE IMAGE BELOW

http://i50.tinypic.com/2irkhnc.jpg

THANKS.

Ice from DW