This is an addon to SuperiorSkyblock2 that makes the plugin use Nashorn scripts engine instead of the default one.
This is mainly used in Java15/16, as these java versions removed Nashorn from being the default scripts engine.
Download link: https://hub.bg-software.com/job/SuperiorSkyblock%20Addons/
If you can't find the modules folder, make sure you upgrade to latest dev build.