You see a lucifuga aranea
Notes
It looks like a Crystal Spider.
This creature can only be found during a mission of The Dream Courts Quest.
Abilities
Melee (0-300+)Damage Taken From Elements
Physical 
Death 
Holy 
Ice
Fire
Energy
Earth
Location
The Haunted Temple under Tiquanda, but only if a player carrying a bait lured it out of hiding.
Behaviour
Fights in close combat. A lucifuga aranea never retreats.
Strategy
The Lucifuga can be as challenging as the Carnivors it spawns with, so it's recommended to clear the spawn or isolate an area with fields when looking for it.