I got a request for a plugin to prevent mob spawns in certain areas. Sure, other plugins can do it, but this is super lightweight with a very straight-forward config. Customize by mob, dimension, and area:
Ghast:
dmz: true
blocked-areas:
0:
level: world_nether
minX: -42
minZ: -42
maxX: 42
maxZ: 42
1:
level: world_nether
minX: -204
minZ: 4
maxX: -138
maxZ: 92