Here is a plugin for building prefabs in Adventure Mode. It allows you to place your prefabs in the world, hand over the resources, and gradually build your structure entirely in Adventure Mode without having to switch to Creative Mode.
LuckPerms is a permissions manager for Hytale. It allows server admins to control what features players can use by creating groups and assigning permissions.
JEI for Hytale. Adds an item recipe viewer with a bunch of extra information about tools, weapons and other items that are not visible in the base game. Basically JustEnoughItems for Hytale!
Region protection plugin for Hytale servers. Define areas, set flags (block-break, block-place, use), and control who can build where. Based on WorldGuard for Minecraft.