Spark of Ice  

If you want to get technical, Its possible for a wizard to use his or her mana to create an large energy void above the mob, this void will strip the energy in the water, and maby even the other gases, Co2,O2, No2, that are in the air, creating ice of various elements. Once that energy is gone the remaining is striped away from the mob, so from the mobs view point its freezing because his energy is being transfered to the reaction. So the spark may be energy and the product of the reaction is endothermic so energy of the enviornment is consumed thus Spark of Ice.