Monsters Level Up is a mod that makes all mobs level up alongside the Player as they progress through the game. Main story advancements will make mobs harder to kill.
The triggers are : Getting Iron Armor, getting Diamond Armor, enchanting, entering the Nether and killing the Ender Dragon.
THIS MOD WON'T AFFECT WORLDS WITH ALREADY ACQUIRED ADVANCEMENTS
Mobs will gain new gears, abilities and behaviors :
Zombies will spawn with armor and swords or axes. They will alert any zombie around them upon getting hit. They can apply the Call Of The Horde effect to the Player, which will make all zombies in an area aggressive. Drowneds will ride nearby dolphins.
Skeletons will spawn with armor and sometimes swords or axes. They will alert any skeleton around them upon getting hit. When a Player is too close, they will pull out a sword or axe, depending on if the Player has a shield or not. They can ride phantoms. Wither Skeletons can sometimes spawn with bows.
Creepers can ride cave spiders or seek a spider upon being attacked by a Player above them to reach them. They will disable shields upon exploding.
Spiders can put Players in cobwebs when attacking.
Endermen can spawn 3 endermites upon dying.
New foes can also appear in the world :
Frozen Zombie
Frozen Zombies are slow zombies that can only spawn in cold biomes. They will inflict the Player with Slowness. They can freeze the water they walk on.
Reanimated
Reanimateds are somewhat fast zombies that will spawn a Skeleton upon dying. They can only spawn if the Player has Iron Armor.
Breacher
Breachers are mini-bosses that rarely spawn when the Player gets Iron Armor. They can dash to reach Players that are far from them. They will inflict the Player with Vulnerability, an effect which makes damage dealt more important. They hold a Breacher Hammer in their hand, which can drop upon death.