Wither, iron golems and snow golems and EnderDragons!
Note: Minify the command to avoid issues :)
Witherstorm statue one command
Advance Mob Spawns!
EVEN MORE SPAWNS!
defeated wither storm
Pet ENDER DRAGON!!!!!
Wither Storm Boss in ONE COMMAND
HEROBRINE COMMAND
HEROBRINE BOSS BATTLE (See YouTube for details)