An illusionist is a wizard specializing in illusion magic. Illusion spells create false images and other sensory tricks. Illusionists can make ghostly sounds to distract opponents, conjure visionary beasts, or create a wall that does not actually exist. Illusionists are a specialty Wizard class.
The power of an illusionist is that the victim feels, and therefore thinks, the illusion is real. Once the combatant realizes the the illusion is fake it holds no power. This is harder than it sounds though for the images invoke strong feelings that support belief of the illusion. When an illusion is still belived to be real it does the same damage as the real subject of the illusion would do.