Shiny Bat

Shiny Bats are VERY, VERY, hard mobs to beat, because of their size, power, and speed. So, it's best to lay around piston and lava traps before entering a new cave. They drop gold/Butter. They are yellow-colored and are hostile. They have Endermen's particles, only colored yellow. You can transform a bat to a Shiny Bat by enchanting an enchanted apple to Smite, Flame, and Infinity, and feeding it to a bat. However, they will still go hostile to you.

Combat
To defeat these is very tricky. You can risk your life by using TNT, or lure them outside to traps. You can also try hitting it, but it will be hard. However, you COULD trap yourself inside a small, cramped hole, and wait it to despawn. They despawn after 3 real life minutes.