Levelled mobs is a plugin that makes it so that mobs can have levels, and depending on the level, the mobs get harder.
link: https://www.spigotmc.org/resources/levelledmobs-for-1-14-x-1-16-x.74304/
ExecutableItems is a item customizer plugin that lets you put potion effects, custom damage values, and special uses on items, /https://www.spigotmc.org/resources/executableitems-1-12-1-16-custom-items-with-simple-gui.77578/