an iron golem type mob that will fight for you and will be biome specific

It would be cool if there was a way to get followers in different biomes that fight for you. perhaps you could find them at a protected structure like a temple. you could free them by getting to their cell and breaking them out. of course there would be a challenge with this. the challenge is that you have to make it past some type of humanoid creatures. these humanoid creatures would try to kill you with some type of maybe throwable tnt or something unique of the sort. this would make it more unique and that would provide a whole new challenge. when you get your follower it will follow you until it gets killed similar to an allay with a block you will not be able to kill it yourself unless you use lava. these creatures will fight against each other so that players can not have more than one at once.