According to Emperor Carpus, the Black Serpent Clan's home was situated in a large system of interconnected caves underneath the deathly ocean floor. The only entrance leading into it was a large X-shaped crevasse.
The radioactive water zone was a natural barrier that prevented trifling marine life from wandering into the Black Serpent Clan's home.
As Vaan scanned the ocean floor for the X-shaped crevasse, he ran into a patrolling black serpent that was minding its own business.
However, when it spotted Vaan, it was dumbfounded and froze in confusion.
(What's a human doing in this region of water? Doesn't he know humans are prohibited from exploring this area?)
While the black serpent was wondering this, Vaan also studied it.
Although the black serpent was also a mutated species that grew several hundred meters big, it only possessed ordinary serpent scales and lacked a golden horn.
