In Hordes of the Things (HOTT) magic has a subtle influence. It will not win you a battle by itself.
It is another weapon in your arsenal which must be co-ordinated with the rest of your army in order to bring you success.
Some other fantasy game systems place a lot of emphasis on magic with powerful mages wreaking havoc over a battle field turning your well drilled legions into a blubbering rabble. This is where HOTT differs. The philosophy of HOTT is based on the many works of fantasy fiction where magic is rarely employed to such a devastating effect on the battlefield.
Generalship and force of arms are the main factors in victory. In most cases the magic acts to target specific individuals or produce effects to affect the morale of the army.
In HOTT magic is like long range artillery targeting individual elements, the effect of magic on the different element types varies with some elements more vulnerable than others.
How the magic manifests itself is not important. It could be a lightning bolt from the sky, the ground could open up beneath the target or it could be some kind of intense psionic attack. All that matters is the effect. The unit may stand and take it, be forced backwards, be destroyed or sometimes flee the battlefield.