This plugin, called "LevelMobs," primarily modifies hostile entities (mobs) upon spawning by assigning them a level.

This level has the following consequences:

Attribute Scaling: Increases the monster's maximum health, attack damage, and movement speed in proportion to its level, with a configurable maximum health limit (100.0).
Equipment: Randomly grants armor pieces (leather, gold, iron, or diamond) and weapons (swords or bows) with enchantments (such as Protection, Edge, or Power) whose strength depends on the monster's level.
Health Bar: Adds a visible name to the entity, showing its level and current health in the form of a health bar (e.g., Lv. 10 ZOMBIE | 50.0/50.0 ❤).
Enhanced Rewards: Upon death, leveled-up monsters drop bonus experience and have a chance to drop extra items (such as iron, gold, diamonds, or experience bottles) based on their level.

The add-on introduces levels in two ways:

Naturally: There is a configurable chance (20% by default) that a naturally spawning monster will receive a random level (between 1 and 30).
By Command: Administrators can use commands to spawn monsters with a specific level.

In addition, the add-on includes a "Horde" system:

A command (/levelmobs horde [level]) allows administrators to summon a horde of 6 to 10 level-matched monsters near them.

There is a small chance (0.5% by default) that a level-matched horde will spawn naturally near a player.

Finally, the plugin provides management commands (/levelmobs and /levelmobs_toggle) to spawn these mobs manually, toggle the natural leveling system on or off, and command autocompletion for ease of use.