So I have two custom zombie classes that are identical using NMS. The only difference is that they are meant to target and attack each other. I'm not going to post the code because it is unneeded as it is exactly this: https://bukkit.org/threads/how-to-override-default-minecraft-mobs.216788/ updated for 1.9 and replacing the targeted entity with my custom mob. Also I have done my own testing. I do not receive any errors when putting in my custom mob and the attacking works if i set it to both the player and a skeleton. It seems to just not want to attack any of my custom entities. If anyone can think of any reason as to why it won't would be much appreciated. At this point I'm pretty stumped and can't think of any other reasons for it to be acting up. I'm sure i'm missing something simple. EDIT: And yes, I am registering the entity as required. Everything works if it is targeting a minecraft entity, just not my custom entity. Thank you in advance.