A unit has to have a Magic Attack to attack magically (duh!) but a unit does not have to be magic to engage in a magic attack (Huh?). We’ll get to that later. Lets do a magic attack. I’m going to click on my home city and double click a wizard looking dude from the Stack List. I see from it’s Army Information Window, that they have a Magic Attack of 25 and a Range of 8. That means they can throw a Magic Attack of 25 points 8 squares away. So I’ll select two Soron Magic Corps and two Southerland Infantry units (Huh?) and move them so they're 8 squares away from the trolls. Do a Select All from the Command Menu then Magic Attack from the Command menu.
Alight, here’s the rule. To perform a magic attack you must choose at least one unit with a magic attack. The target must be with in range of every unit that contributes to the magic attack. The spirits of non-magic units such as Southerland Infantry can be brought along and used to defend against the counter attack but do not contribute to the magic attack in an offensive way.