So I helped my friend add this plugin to his server and the cool thing is you can customize the mob drop after defeating them and make boss eggs for the shop as well. I think this might be interesting to see on Skyblock. https://www.spigotmc.org/resources/►►custom-bosses◄◄-make-your-own-bosses-now.15646/ Plus you can make it where one of the boss drops can switch out the dragon egg challenge.
It is availabe in skyblock but it is bugged Hahah You cna just warp there but no boss will spawn Hope it will be fixed soon