Bal

 is a boss that spawns every 5 minutes if a player is nearby.

Spawning
The Bal spawns about every 5 minutes in the middle of Khazad-dûm, which can be found anywhere in the lower Y levels of the Crystal Hollows. When the previous Topaz Crystal disappears, the Bal will appear in the center as an expanding magma cube.

Drops
Upon being hurt, the Bal has a chance to drop items on the ground similar to how items are dropped from Ender Dragons. These items can be:
 * (rare)
 * (rare)
 * (rare)
 * (rare)

Behaviour
Bal will hop around the arena, summoning Fire Bats and Blazes to attack the player while shooting fireballs. In addition, it will deal contact damage like a normal Magma Cube. These attacks deal low damage, with the Fire Bats and Blazes easily ignoring the player if they have an Intimidation Talisman or better.

Upon being defeated, it will return to the middle and slowly shrink into nothingness. After that, the Topaz Crystal will appear nearby.

Dialogue

 * You cannot best me!
 * Grrrr! You won't be able to hit my Fire Bats!
 * Bah! Come forth my minions! Fly above, take them out!
 * AGGHHHHHHHHHHH!

Upon damaging Bal to certain health thresholds:

Around 75% health:


 * The bosses outer shell looks to be weakening!

Around 50% health:


 * Half way there! The boss is starting to become weaker!

Around 25% health:


 * Nearly there! The boss is shaking it can't last much longer!

Upon defeating Bal:


 * The boss looks weak and tired and retreats into the lava...

Trivia

 * The Bal is based on the Balrog from J. R. R. Tolkien's Lord of the Rings legendarium.
 * Its spawning place, Khazad-dûm, is also based on the place of the same name.
 * It used to be possible to trap Bal by building a cage around its spawn point, but building in Khazad-dûm is now restricted in order to prevent it.