You see mystic energy.
Notes
These creatures are actually invisible, but they cannot be looked at and spawn on top of the Mystic Energy objects that look like electrical sparks. Despite not being possible to target them, they can be killed by convinced Rift Fragment's AoE Drown Damage attack.
They are encountered during the fight against Ascending Ferumbras during the Ferumbras' Ascension Quest.
Abilities
Melee (0-?)
Fire Missile (300-500+)Damage Taken From Elements
Physical 
Death 
Holy
Ice
Fire
Energy
Earth
Location
Behaviour
They are fixed in position, unable to move.
Strategy
Avoid staying next to them as they seem to attack more often in close range, possibly with melee attacks.