Fatima spent the entire night explaining the gun's 13th function. After that, she started explaining the theories and the process of activating it in the proper way. However, after I listened to all of it, I quickly realized why Fatima flatly replied "No" when I asked for a clue.
"... The methods are completely different..."
To activate the 13th Form in the normal way, you would need to first insert a sliver of your soul into the gun's core. Then, after that, you would need to mold that into a semi-conscious will. That "will" would then become the gun's "soul" and earn the right to become a Mechanical Lifeform.
"It's like creating a Nascent Soul in the cultivation stories I've read..."
I felt tired just imagining the process for that. After all, I'm no cultivator and had absolutely no idea how to split off a small part of my soul to use in the said process. Much less how to nurture it into becoming a conscious entity.
