Despite looking like a jumble of letters it's pronounced "Nero".

#10 of the 27 Dead Apostles.

His human name is Forbro Rowain. He is a graduate of the Wandering Sea Magic Society who had been transformed into an immortal by a sorcerer in his search for immortality.

Unlike ordinary immortals, who directly take in beasts as part of their bodies, he has internalized and muddled the 666 elements of beasts into his body, creating chaos within his body.

This is why Nero calls himself the primordial sea.

His unique ward is the “Beast King's Nest.

He maintains the primordial sea by expanding the inherent boundary inside his own body (in the form of a human being) (it is thought that such a large number of humans are needed as energy for this purpose).

Please do also check Neco-CHAOS!