Have you ever wanted endermen that were harder to fight if not this in not the place for you. If you do want this addon then you have accepted the challenge. (This is my first addon that I have ever published but it's not my first addon made because I have a secret addon that I am keeping to myself)
This addon is only for people who like a challenge so I changed the behavior in endermen so they are harder to fight.
Enderman info

I gave endermen a hivemind so if you hit one then it will call to other endermen in a 100 block radius to come help it fight you so don't hit one while you go to the end because it lasts for 50 seconds and you will be swarmed by endermen. Don't look at them either or you will be challenging all of them at once. The end is now a very hard challenge so prepare and good luck you will need it when you are lost to the sea of endermen. They also steal items you drop and use weapons/armor (have not rendered armor) so if you don't want this then keep mob griefing off.

I attacked one and all the nearby enderman attacked me.

They thirst for blood.