Idea for a new mob: The Abyss

The Abyss is a mob that spawns in the Nether. It has no arms or legs and it has a pitch-black face with two glowing white eyes and a purple cloak. It will not harm the player.

If you hit is, its cloak will be removed, it will become aggressive and it will start shooting balls of smog at the player. 

If the player defeats the Abyss, it drops an item called the "Ghost of Abyss". If the player smelts the Ghost of Abyss in a furnace, it becomes an item called the Ghost Ingot, which you can then use to create tools, armour and blocks.