You see a blood tear.
Notes
Part of The Secret Library Quest.
Abilities
Unknown.
Damage Taken From Elements
Physical 
Death 
Holy 
Ice 
Fire 
Energy 
Earth 
Location
Ghulosh's room inside The Secret Library.
Behaviour
They retarget very often.
Strategy
They shouldn't be your focus during the fight but eventually you'll have to kill them to clear the room.