You see a furious fire elemental.
Notes
Furious Fire Elementals are entities consisting only of fire. They have been spotted in a cave in Hellgate where it's far too hot to survive for very long. Part of The Repenters Quest.
Abilities
Damage Taken From Elements
Physical 
Death
Holy
Ice
Fire
Energy
Earth
Drown
Behaviour
A furious fire elemental attacks in melee range. A furious fire elemental never retreats.
Strategy
Kill them quickly before they can deliver too much damage. It is recommended to run towards them, since they do their distance attacks less often.
History
Before Winter Update 2016 it was named fire elemental.