This mod allows to spawnproof areas of 64x64x64 blocks with just one end crystal (cubic, not spherical).

Each crystal you place in the world creates an area that starts from the block it is placed to 64 blocks above vertically and 32 blocks in each horizontal direction (north, east, south, west). This is mainly because it is easier to hide it below the surface you want to spawnproof.

Now is possible to rename crystals to avoid every crystal in the world be affected by this behaviour.

You can modify this configuration in the file crystal.properties that is created in your .minecraft folder.

To clarify some doubts about how lower-limit and crystal-name config variables works:

The lower-limit option specifies the bottom distance between the affected area and the block where the crystal is located (one above the obsidian).

By default it is set to 1 so that the last layer affected is the one below the end crystal (the obsidian one).

If you set it to 16, the area wil be lowered 16 blocks from the crystal. This will not expand the affected area, just move it in the Y coord.
The crystal-name property is meant to be used when you want to make only certain crystals to be able to spawnproof. Basically leaving it blank will make every crystal to be spawnproofing. Writing some word (or words) like "spawnproof" (spaces also allowed) will force players to rename crystals with a nametag named "spawnproof" to make them spawnproof their surroundings.

This is made for example if you want to have decorative crystals near farms where you need mob spawning.

The original idea of this concept is made by ethnographie and you cand find her datapack here.

Mob proof crystals