The Exchanger

The mob that I feel would fit right into the Minecraft world would be the exchanger ( Not a permanent name) This mob will spawn exclusively in the end. It will spawn alongside the endermen but, will spawn less frequently. Like a zombie pigman it will be fast/dangerous and passive until hit but, if you hit a enderman it will also start attacking you to protect its friend.
A neat part about the new mob is that it has a chance to teleport you back to the main world on death. This will cause you to lose all progress done on the dragon. This means all players will have to be more careful when killing the dragon giving the boss battle a much needed difficult boost. It would look like a hovering stray (no legs) with a purple cloak. Also the mob drop could be a blueish purple item that has the structure of a slime ball called a ?. When combined with chorus fruit it could make another item.
I would be looking forward on seeing the community’s feedback!