You may get to Hadum Boss Rush after completing the Elion Boss Rushes to increase CP.
Hadum Boss Rush for each boss will unlock once you complete Lv 99 Elion Boss Rush for the relevant boss.
You may think it time consuming to complete up to Lv 99.
You can skip over 5 levels at a time in Elion Boss Rushes.
We recommend using Black Pearls to exchange the Boss Stamps for bosses of your choice to complete up to Lv 99 more quickly.
If the Combat Plus item is active, you can challenge the next level even if you proceed with auto Boss Rush,
and you can complete Boss Rushes more quickly as you'll skip to the boss.
However, multipliers will increase by x10, so we recommend checking Min Multiplier before proceeding.
Also, if Combat Plus is active when progressing Hadum Boss Rushes later,
entry multipliers will increase by 10 times, allowing you to complete them more quickly.
Less time will be required for Boss Rushes, and you can use more time in adventuring.
Last, we recommend that you exchange all Boss Stamps when you have the most bosses unlocked for Hadum Boss Rush.
More EXP is required for higher Boss Rush Knowledge levels. When you don't have many bosses available for Hadum Boss Rush,
exchanging all Boss Stamps at once will eventually lead to the latter bosses having a relatively lower Knowledge level, resulting in a net decrease in CP.