As one of the most important innate skills of a fighter, passive skills play a central role in fighter synergy and battle planning. Just like the actively used special skills, passive skills can be leveled up through a process called splicing. Splicing passive skills will enhance them, greatly increasing your strength on and off the battlefield.
Fighters can use Passive Splicing to enhance their innate genetic abilities, leveling them up.
Example: Fighter A has passive skills "Skill A" and "Skill B". Fighter B has passive skills "Skill A" and "Skill C".
If you try to splice Fighter B's genes and passive abilities into Fighter A, then Fighter A's "Skill A" will gain experience, and when it gains enough, it will level up to the next level.
As much of its genetic potential has been spliced into the genes of another, Fighter B will lose all its abilities, and become an ordinary survivor, and never again will it fight on the battlefield, and will become an ordinary citizen to be protected by the newly-strengthened Fighter A.
The amount of experience required to level up a passive skill increases as the passive skill reaches higher level. If you splice genes from a Fighter whose passive ability has already been enhanced, the amount of experience it offers is increased as well：