You have 5 weekly attempts per family to defeat bosses of the Black Shrine. If you successfully defeat the bosses at each difficulty, it will be deducted from your total count. (Resets at Midnight on Sunday)
If a boss at a certain difficulty is successfully defeated, the number of attempts will not be deducted even if you challenge them again with the same character, at the same difficulty.
Note that the number of attempts will not be deducted if you are defeated or forfeit.

If all five weekly attempts have been used, you can continue to challenge the levels you've successfully cleared, and your highest record will be reflected in your Boss Blitz ranking.
Please note that these conditions apply only to the same character who has successfully defeated a boss. If you proceed to defeat the bosses with a different character, it will be deducted from your total number of weekly attempts.

The Black Shrine offers 10 levels of difficulty, called calamities. From Calamity 1 to Calamity 10.
The higher the boss’ difficulty, the more diverse its attack patterns are, and the greater the potential for better loot and rewards.

Boss battles are recorded based on the level of difficulty, and by class.
When a Black Shrine boss is first defeated on each difficulty level, and by each class, the name of the Adventurer (that first defeated the boss at each difficulty level) is announced throughout the world of Black Desert.
Calamity 1 to 5 bosses are open to all classes.
Calamity 6 to 10 bosses will only unlock if an Adventurer successfully defeats the boss of the previous level. This is applied for each class separately.

◈ What Are Light Orbs? Boss Blitz Guidelines

These are points that can be obtained while completing the main questline for LoML and are closely related to the attributes of each boss.

Before delving into light orbs, it is necessary to understand how stats are applied in the Black Shrine boss encounters.

• The bosses of the Black Shrine receive/deal damage based on a ratio of 90% aura attribute and 10% character attack/defense power.
• Only 10% of the skill add-on effects and buff effects related to the character’s AP/DP are applied.
• Only critical hits from attribute attacks are displayed during the boss blitz. (Critical hits based on the character’s existing stats are applied, but are not displayed.)
• The critical hit rate for attribute attacks is applied at 50% during the boss blitz.
• All debuff resistance is applied at 20% during the boss blitz. (Resistances that have been increased due to a character’s existing stats are not applied.)

Therefore, it is extremely important to obtain and utilize the orbs acquired during the main questline to increase aura stats for a confident victory!

Adventurers can check the sun/moon/earth attribute weaknesses of each boss and invest in the auras/attributes that the boss they wish to take down is weak to.

Investing a light orb increases attack power (AP) by 50 and defense power (DP) by 100 for that attribute/aura each time you invest one, and it grants you 3 additional stat points. 
Additional stat points can be invested in attack power or defense power at the Adventurer's discretion. 

The screen below is what you can see when you click '② Manage Aura' in the image shown earlier above. In the UI, you can see the number of light orbs you have and their investment status.