Hey Lycanite ,
I've got an little idea for the special mobs (lunar , light , celestial mobs) about one specialy , the Khalk.
My idea is to make a mini-boss Khalk (like Lunar Grue) that can be named Incandescent Khalk , Fiery Khalk , or something else.
It would be 3 times bigger than a normal Khalk , and got around him a "fiery aura" that burns the player .
It would be a black-obsidian textured Khalk but when he attacks you the shell will burn ?
he can spawn 2 khalk to help him .
Also he can breaks blocks around him to clear the zone?
that's all ... not a very good idea , i know , do what you want to do but a mini-boss Khalk would be awesome !