how do you dealing with black dragons as a mage ?

[Ryastar]

Personally, since you already have dryads, and probably anga's ruby then, i would add sprites to your line up. They are quite amazing little fighters. If you can't find sprites, consider lake fairies, though they aren't near as good as sprites. I would recommend those units in place of the knights. Another thing i would recommend is red dragons for your green ones, at least for the land of the dead. Red dragons are tough and deal a lot of damage, without the total spell immunity that hampers their black cousins. They are ALWAYS available in the land of the dead, in the set off ridges near Karador's castle (black dragons are also around there, but i don't recommend them as highly).