Crimson Splitjaw

The Crimson Splitjaw (Benikuchinawa ベニクチナワ) is a giant red snake species that live primarily in the third layer's steep cliffs.

Description
By spreading its hood it is able to swiftly surf the air currents. Sometimes they might fly up to the upper layers in search of food, but it is exceedingly rare to see them in the most shallow sections of the abyss. They have vestigial eyes and many wart-like appendages on their lower jaws.

Whether it's to harvest the nutrients, or to temper the gizzard is unknown, but they are known to habitually swallow relics and minerals. There is no doubt that the sac of any of them bears treasure in great quantities, though the possibility of it being defecated cannot be crossed out either.

They're ferocious predators that attack any delver on sight, so their danger level is high, standing as some of the most dangerous creatures on the third layer. Their meat is edible, but it's not very tasty.

Trivia

 * In the manga, while traversing the 3rd layer, Reg and Riko stumbled upon an ancient ship buried in the side of the cliff. Upon investigation, it turned out to be the lair of the same Crimson Splitjaw that had attacked Riko before she found Reg. This was changed to a Madokajack's lair in the anime.