Upon first coming within Magic meters of you, creatures are automatically subject to one of your attack forms, which must be available to you and decided upon when Lethal Impression is bought. This is a free action out of the normal sequence. All normal combat modifiers apply, and targets will often be surprised.
Examples of this is the nauseating stench of the a ghast, the withering of the ghost or the gaze of the medusa. You can turn this power off, but it takes some special effort (such as a mask, strong musk, robing yourself etc.). With an extra schtick pick, you can turn it off at will.