For most living beings in this world, the brain—or the central nervous system, or ganglia... it has many names. Whatever you call it, it's the organ that controls the body, gives it commands, and makes you feel 'I can totally do that!' whenever you see something, only to have every part of your body retort, 'No, you can't!' For anyone, it is an incredibly obvious and exceptionally fatal weak point.
It's not just that getting it destroyed is bad. Most of the time, just a small jolt, a bit of electromagnetic interference, or even a slight increase in temperature will cause it to immediately crash and stop working. This thing is truly delicate, and even for Transcendents, it's a major liability.
But despite all these disadvantages, the brain is still extremely important to most life forms. At least for Cultivators at the Extraordinary Tier, their second cognitive organ, the Soul, is still far from being able to completely replace the brain.
