Murderous Mage

I'm not going to boast, but it's fact that i know the most about these creatures. They are the most dangerous mages on the face of the earth. They have a temper where if you even welcome them or offer them help, they will kill you. I will now explain how they do this. They chant a word that i cannot reveal for safety reasons, and use a complicated hand pattern in the air. They then leave. The cursed gets a horrible stabbing feeling in the head, which they assume is a migraine. A few days later, blood erupts from the mouth and the head simply explodes. Their is no cure. These mages are as common as rats, but live in active volcanoes. For obvious reasons, no one has ever spoken to one of these mages. They can be apocalyptic in large numbers, but only very deadly in ones.