Stonevaults is a Fabric mod that adds unfriendly jigsaw structures.
Stonevaults depends on Fabric API and Cloth Config.
All structures present in this mod are jigsaw structures that make use of template pools and processors as well as structure files. There isn't a ton of easy to understand information about creating jigsaw structures but TelepathicGrunt's StructureTutorialMod is very helpful for understanding how they work.
This mod is available under the MIT license. You are free to port, modify, use it as you wish.