Control the Light Level for Mob Spawning!
/gamerule mobSpawningLightLevel
Only needs to be installed on the server!

This mod adds the game rule /gamerule mobSpawningLightLevel, which allows you to change the light level at which hostile mobs can spawn in the world. Now you can configure mob spawning so that they appear only in complete darkness or even in well-lit areas!
Mobs spawn only at light level 0
Mobs spawn at light level 7 and below (default settings)
Mobs spawn at light level 10 and below
Mobs spawn at any light level