Are you blind? Its Skeletron's corpse! - Skales' spawn message
Skales is another counterpart of Skeletron and a boss in the Lunar Age mode.
The goal in phase 1 is to destroy all the crystals on Skales' hands. This is extremely difficult because Skales will spawn Earth Snakes which will take away 5 damage when you touch them. His head does not take damage until phase 2.
In phase 2, Skales' hands and arms are wiped out leaving only his head left. It will knock him on the ground so hard, he is put into a daze. Oblivion Slimes will come out of trapdoors and try and hurt you. Every 5 seconds, Skales will wake up out of his daze and fly up into the air, and pick a target to slam down on you. This time, Skales is vulnerable to all your attacks which means you have to attack the crystal on his forehead.
He shares the same boss theme as the Brain Of Cthulhu. Phase 2, he has his own boss theme called Snow's Blind. Which is the Lunar Boss theme simpily sped up by 12.