PolyPack is a server modpack which is made to be played with a 1.16.4 vanilla client.
It aims to add as much quality modded content as possible and currently adds new biomes, structures, tools, weapons, blocks and dimensions.
PolyPack does not replace any vanilla content.
It does so by utilising the PolyMc mod and the resource pack it generates as a compatibility layer between the vanilla client and the modded Fabric server.
For the new blocks and items to properly display, each person connecting to the server must accept the server resource pack.
As PolyMc adds more features this modpack will continue to expand with new content. Not all features of the currently included mods are available yet but as PolyMc improves they will be enabled.