Adds "Mob density" and "Limit mob density" settings you can use to reduce the overall number of mobs you encounter.

"Mob density" will scale the number of mobs to the percentage set there. So if you set it to 50% then all zones will only have 50% of the mobs they have by default.

"Limit mob density" sets the maximum number of mobs you encounter in any zone. So if you set it to 50% then those zones that have mob-densities over 50% will be set to 50% (zones that are already below 50% will by unchanged and remain as they are by default).

Normally (when it's just some zones that you think have too many mobs) you will want to use "Limit mob density" but you can use "Mob density" to just make the overall game lighter on mobs.