I have a very small server running forge 1.12.2 and am looking for a mod that will prevent mobs from spawning in a set area. I used to use Forge Essentials when my server was running 1.7.10 but i am updating to 1.12.2 and that mod is no longer being maintained. Is there another similar server side mod like Forge Essentials?
It's a little hard to find in the wiki, since there isn't really an example for it, but it supports specifying x/y/z ranges with a "position" rule, so as long as the player built town can be covered by a cuboid (or a few possibly-overlapping cuboids), that should meet your needs. I haven't used Forge Essentials, so I don't know if it supported defining a more complicated region shape.
The position doesn't really describe what would be x,y,z, and if it would cover from build limit to bedrock. The documentation on that mod is very lacking. Is there any other mod that could do what i am looking for?