This is a boss class creature.  So far It's being called the Poison Flame Drake.  It gets it's name from the violet flame it emits which does little incendiary damage compared to normal flames, but instead inflicts a life draining poison through the singed skin.  It produces this flame by spitting flammable gasses from an opening in it's throat and snicking the tips of it's tongue together to create a spark.  It also has a powerful tail, bite, and set of claws.  An average sized person would be a bit taller than it's shoulder.