CeiOakmage

I'm trying to complete a section in the easy part of the Falador quest diary. Heal an elemental mage. How do I do this? I tried shooting one of them with the proper elemental spell and all it did was make them fight me. does anyone know what I need to do to complete this one? It says to cast an elemental spell on the the wizard of the same element, but I'm not sure what they mean by that.