This works flawlessly... I don't normally rate resources, this is an expetion. I've been trying to find a feature or have someone design a feature like this for months. I don't know Java or anything in order to make it myself but spent a while researching how it would be done. This is perfect and everything I wanted.
If you run an rpg server. Download this, config it and enjoy it.
It's 100% worth 5 bucks, but the dev is kind enough to offer those 2 links as well.
Update: the dev is kind enough to answer questions via private message... And even try and help you when you are just being an idiot. (make sure you are using the correct mythic mobs)