Minecraft wiki entry for Creating_a_challenge_map, associated text: Also, you could spawn an ender dragon or a wither in a room. Just remember to use the command /gamerule mobGriefing false, so that the bosses won't be able to destroy blocks. Alternatively, add your own boss. Customize your own boss mob by adding extra data tags (see Tutorials/Command block#1.7 uses). Even better, create custom mods with your own made-up boss! NOTE: To do this, you must be able to use Java programming or data packs (see Tutorials/Creating a data pack).Also, you can download Mods To make bosses even better!