You see a reflection of a Mage.
Notes
It's somehow related to the Raging Mage and very similar to it in power.
Part of the Opticording Sphere Quest.
Abilities
Melee (0-30+)
Fire Missile (0-200+)
Mana Drain (0-100+) Shoots Fire Bomb
Summons (1 Golden Servant)
Rage of the Skies (0-?)Damage Taken From Elements
Physical 
Death
Holy
Ice
Fire
Energy
Earth
Location
Behaviour
Attacks at close range and runs at very low HP.
Strategy
It's very weak and shouldn't pose any threat if you are planing on killing the other bosses that spawn in the same room.