You see a hibernal moth.
Notes
It can be tamed using a Purple Tendril Lantern.
Abilities
None.
Damage Taken From Elements
Physical 
Death 
Holy 
Ice 
Fire
Energy
Earth
Drown
Location
Court of Winter at night.
Behaviour
The Hibernal Moth will follow and target other wild creatures, but will not be attacked by them. It's very weak and not a real threat.
A hibernal moth attacks in melee range.
Strategy
If your purpose is to tame it, clear the spawn around it (carefully not to kill the Hibernal Moth), and then just use the Purple Tendril Lantern on it (it will run most times). It's very easy to kill and will die before the other creatures it spawns with.