Note to servers using 1.10 or older: You must set 'use-subtitles' to false in the configuration file! Doing otherwise is not supported.

Mobs now have an experience level. The further they are from spawn, the higher their level. If their level is greater than your vanilla experience level, they deal more damage and takes less. They will also yield more experience if you kill the mob yourself. The end result: mobs serve as your world border.

Even if the members on your server are crazy enough to enter regions way above their level, they will die much more easily and have a hard time doing much of anything against the monsters.

The mob buff is based on the difference between your level and the mob level, not their proportions. In other words, a level 1 player vs a level 3 mob is the same as a level 21 player versus a level 23 mob.

For what it matters, the display is quite fancy.

Configuration Settings:

• Mob health, damage and experience value: You can change the proportions as you see fit. By default, they gain a quarter of their default health, damage and experience for every level.
  
• Experience cap: Apparently offering massive bonuses to experience for venturing far out is kind of self-defeating. You can now limit the gain to whatever you please. By default, mobs never drop more than double experience.
• Speed and sightlines: Mobs can spawn with stronger attributes if you travel far enough. These are disabled by default, since it can't single out a single player.
  
• Clones: If traveling far enough, a mob may spawn double, triple or quadruple. These mobs will always despawn, and do not drop any items - only experience.
• Failsafes: In case a player travels way farther than they reasonably could, failsafes allow you to turn up the heat. They include making neutral mobs hostile, regular bursts of damage, hunger draining, no regeneration, and instant death.
• Level caps: Set a power limit to all of these effects, if you want all regions to be fair and playable.
  
• PvP: Comes with a special PvP mode. This means vanilla experience gives more health and damage, but only up to the local mob buff. Note that this is untested, can be very overpowered, and will encourage players to move far away from spawn to get the full effect. It's off by default.
• World settings: You can customize worlds to your liking, expanding and contracting the mob border as you see fit. You can set a default level, a grace area where mobs don't level up (like spawn), and most importantly how quickly the mobs level up.

This plugin is not for everyone, as it does not feel like Vanilla nor fit in with other big plugins.

Known bugs:

• mcMMMO unarmed skill is overpowered, as its +3 damage from the get-go can't be changed by this plugin.
• Deflected ghast fireballs deal normal damage.

Feedback is appreciated.