While reborn characters are incredibly powerful, those who have passed the trials of a second rebirth are nigh invincible! The quest to be reborn a second time has many tricks and trials which characters must pass to succeed. Thus, it has very high prerequisites:

Requirements: Characters must be level 120 or higher. Characters must have already been reborn once (are 1st rebirth characters.)

Those who choose to take the quest for second rebirth will have to destroy mountains, kill hordes of monsters and even defeat Satan himself in a duel to the death.
Bearing in mind the difficulty of the quest, it pays to take friends with you on the journey -then you can help them get reborn too!

Note: When bringing friends with you on the second rebirth quest, make a team of which you are the leader. Remember to pick the important items yourself, and initiate all the dialogues pertinent to quest completion by yourself.