Molten Bosses are bosses in the Lunar Age.
The Molten Queen is a OP version of the Snow Queen. Her attack, speed and health has doubled since the last fight.
The Molten Brain is a OP version of the Brain Of Cthulhu. His attack, speed, health and fight is the same as Skeletron Prime but he has Arch Wyverns instead of hands to attack.
The Molten Golem is a OP version of Golem. His attack, speed and health has doubled since the last fight. He can give you the On Fire! buff.