EZMobSpawns is a utility mod that adds an independent mob spawning system to Minecraft in order to provide users with better control over how, when, and where mobs spawn. It provides consistent spawn rates across different biomes (both modded and unmodded), as well as a wide variety of configurable properties to customize mob spawns and spawn mechanics.
EZMobSpawns accepts json files in the config directory that start with the prefix ez_mob_spawns.
See the demo config for an example of how to get started.
For more information on the config format, see the JSON Configuration doc here.