The Ice Mage is a ghost like hostile mob that spawns in a unique fortress: The Frosted Fortress.
It uses its frozen staff to throw and spread freezing ice magic at you, Pretty annoying, The Fire Mage does the same, It seems to be a black ghost like humanoid entity wearing a blue coat with blue, cyan, and even black markings on the coat, it also has light blue eyes, She was infected before the Player joined the Minecraft Multiverse.