Frost Guardian

Frost Guardian
 Design:  A large icy skull with an appearance similar to Skeletron

 Spawning:  Use the frozen skull in the ice biome at night

 Stats:  Health: 5,000 Attack: -40 Melee -60 Headspin -30 Ice skull (+2 seconds of slowness or frostbite) Defence: 25 (15 while spinning)

Attacks: -Flies around the player, firing ice-covered skulls at them every 2.5 seconds. Every 10-12 seconds the Frost Guardian's skull will begin spinning towards the player for 8 seconds, moving a bit faster than skeletron's version of this attack.

Hardmode Variant
-Upon beating the wall of flesh this boss will become stronger and gain different attacks as long as it has been defeated at least once in it's pre-hardmode form

Stats: Health: 30,000 Attack: -70 Melee -80 Headspin -45 Ice skull (+2 seconds of slowness and frostbite) Defence: 50 (30 while spinning)

Attacks: -Flies around more unpredictably as well as firing off skulls every 2 seconds instead of 2.5. Also spins much faster, being about twice as fast as skeletron's spin attack

Expert Mode:
Pre-Hardmode Stats: Health: 7,000 Attack: -50 Melee -100 Headspin -40 Ice skull (+2 seconds of slowness or frostbite) Defence: 25

-Fires every 2 seconds when not spinning, spins 75% faster than skeletron when spinning

Hardmode Stats: Health: 37,500 Attack: -80 Melee -120 Headspin -60 Ice skull (+3 seconds of slowness and frostbite) Defence: 60

-Fires skulls every 1.75 seconds and spins 150% faster than skeletron