The impostor addon adds a sus impostor they naturally spawns in the world. The impostor does a massive amount of damage and is a great addition to mob farms. The sus imposter has only 1 hp, but don't let that fool you, his damage makes up for it.

Where will it spawn?

The impostor will spawn in light levels of 7 or less. He is less common than normal monsters so you will have to try a little harder to find him!

What does it attack?

Created By Outer Cloud Studio 

The impostor will attack all passive mobs, hostile mobs, and players! Be warned as the impostor is faster than a normal walk speed!

Double click on the file to open it and Minecraft and then enable all experimental settings and enable the add-on under the behavior tabs.

creator: https://twitter.com/CloudOuter